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DEI - shares	3 Months Ended
DEI - shares	Mar. 31, 2015	Apr. 30, 2015
Document and Entity Information [Abstract]
Entity Registrant Name	Five9, Inc.
Trading Symbol	FIVN
Entity Central Index Key	0001288847
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Document Type	10-Q
Document Period End Date	Mar. 31, 2015
Document Fiscal Year Focus	2015
Document Fiscal Period Focus (Q1,Q2,Q3,FY)	Q1
Amendment Flag	false
Entity Common Stock, Shares Outstanding		49,837,098

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2015	Dec. 31, 2014
Current assets:
Cash	$ 50,646	$ 58,289
Short-term investments	19,999	20,000
Accounts receivable, net	8,719	8,335
Prepaid expenses and other current assets	3,170	1,960
Total current assets	82,534	88,584
Property and equipment, net	12,426	12,571
Intangible assets, net	2,425	2,553
Goodwill	11,798	11,798
Other assets	863	1,428
Total assets	110,046	116,934
Current liabilities:
Accounts payable	2,541	4,179
Accrued and other current liabilities	8,107	7,318
Accrued federal fees	7,531	7,215
Sales tax liability	1,221	297
Notes payable	3,528	3,146
Capital leases	4,467	4,849
Deferred revenue	5,641	5,346
Total current liabilities	33,036	32,350
Revolving line of credit	12,500	12,500
Sales tax liability — less current portion	2,303	2,582
Notes payable — less current portion	21,698	22,778
Capital leases — less current portion	4,560	4,423
Other long-term liabilities	748	548
Total liabilities	74,845	75,181
Commitments and contingencies (Note 10)
Stockholders’ equity:
Preferred stock, $0.001 par value; 5,000 shares authorized, no shares issued and outstanding at March 31, 2015 and December 31, 2014	0	0
Common stock, $0.001 par value; 450,000 shares authorized, 49,612 shares and 49,322 shares issued and outstanding at March 31, 2015 and December 31, 2014, respectively	50	49
Additional paid-in capital	172,637	170,286
Accumulated other comprehensive loss	(1)	0
Accumulated deficit	(137,485)	(128,582)
Total stockholders’ equity	35,201	41,753
Total liabilities and stockholders’ equity	$ 110,046	$ 116,934

Condensed Consolidated Balance Sheets - Parenthetical - $ / shares	Mar. 31, 2015	Dec. 31, 2014
Statement of Financial Position [Abstract]
Preferred Stock, par value	$ 0.001	$ 0.001
Preferred Stock, shares authorized	5,000,000	5,000,000
Preferred Stock, shares issued	0	0
Preferred Stock, shares outstanding	0	0
Common Stock, par value	$ 0.001	$ 0.001
Common Stock, shares authorized	450,000,000	450,000,000
Common Stock, shares issued	49,611,533	49,322,000
Common Stock, shares outstanding	49,611,533	49,322,000

Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Income Statement [Abstract]
Revenue	$ 30,274	$ 24,274
Cost of revenue	14,778	13,148
Gross profit	15,496	11,126
Operating expenses:
Research and development	6,038	5,225
Sales and marketing	9,931	9,022
General and administrative	7,275	6,171
Total operating expenses	23,244	20,418
Loss from operations	(7,748)	(9,292)
Other income (expense), net:
Change in fair value of convertible preferred and common stock warrant liabilities	0	1,745
Interest expense	(1,139)	(778)
Interest income and other	2	32
Total other income (expense), net	(1,137)	999
Loss before provision for income taxes	(8,885)	(8,293)
Provision for income taxes	18	27
Net loss	$ (8,903)	$ (8,320)
Net loss per share:
Basic and diluted (in USD per share)	$ (0.18)	$ (1.48)
Shares used in computing net loss per share:
Basic and diluted (in shares)	49,433	5,608
Other comprehensive loss:
Change in unrealized gain/loss on short-term investments, net of tax	$ (1)	$ 0
Comprehensive loss	$ (8,904)	$ (8,320)

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Cash flows from operating activities:
Net loss	$ (8,903)	$ (8,320)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,775	1,592
Provision for doubtful accounts	113	20
Stock-based compensation	2,235	1,196
Loss on the disposal of property and equipment	10	0
Non-cash interest expense	84	51
Changes in fair value of convertible preferred and common stock warrant liabilities	0	(1,745)
Others	(1)	0
Changes in operating assets and liabilities:
Accounts receivable	(510)	344
Prepaid expenses and other current assets	(1,211)	(965)
Other assets	(94)	(65)
Accounts payable	(1,629)	(221)
Accrued and other current liabilities	1,123	875
Accrued federal fees and sales tax liability	960	523
Deferred revenue	286	582
Other liabilities	9	(47)
Net cash used in operating activities	(5,753)	(6,180)
Cash flows from investing activities:
Purchases of property and equipment	(198)	(71)
Decrease (increase) in restricted cash	660	(25)
Purchase of short-term investments	(20,000)	0
Proceeds from maturity of short-term investments	20,000	0
Net cash provided by (used in) investing activities	462	(96)
Cash flows from financing activities:
Payments for deferred offering costs	0	(805)
Proceeds from exercise of common stock options and warrants	116	556
Proceeds from notes payable	0	19,561
Repayments of notes payable	(781)	(264)
Payments of capital leases	(1,687)	(1,282)
Net cash provided by (used in) financing activities	(2,352)	17,766
Net increase (decrease) in cash and cash equivalents	(7,643)	11,490
Cash and cash equivalents:
Beginning of period	58,289	17,748
End of period	50,646	29,238
Non-cash investing and financing activities:
Equipment obtained under capital lease	1,309	769
Equipment purchased and unpaid at period-end	16	20
Deferred initial public offering costs incurred but unpaid at period-end	0	1,787
Net cashless exercise of preferred stock warrants to Series A-2 convertible preferred stock	0	509
Vesting of early exercised stock options	$ 0	$ 28

Description of Business and Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business and Summary of Significant Accounting Policies	1. Description of Business and Summary of Significant Accounting Policies Five9, Inc. (together with its wholly-owned subsidiaries, the “Company”) is a provider of cloud contact center software. The Company was incorporated in Delaware in 2001 and is headquartered in San Ramon, California. The Company has offices in Europe and Asia, which primarily provide research, development and client support services. Basis of Presentation The accompanying condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States (“GAAP”) and applicable rules and regulations of the Securities and Exchange Commission (“SEC”) regarding interim financial reporting. Certain information and note disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. Therefore, these condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and notes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2014. All intercompany transactions and balances have been eliminated in consolidation. Use of Estimates The preparation of consolidated financial statements in accordance with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenue and expenses during the reporting period. The significant estimates made by management affect revenue, the allowance for doubtful accounts, intangible assets, including goodwill, loss contingencies, including the Company’s accrual for federal fees and sales tax liability, accrued liabilities, stock-based compensation, fair value calculations of the convertible preferred and common stock warrant liabilities, provision for income taxes and uncertain tax positions. Management periodically evaluates such estimates and they are adjusted prospectively based upon such periodic evaluation. Actual results could differ from those estimates. Significant Accounting Policies The Company’s significant accounting policies are disclosed in its Annual Report on Form 10-K for the year ended December 31, 2014. During the three months ended March 31, 2015, there were no changes to our significant accounting policies. Recent Accounting Pronouncements In April 2015, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") No. 2015-05, Intangibles - Goodwill and Other - Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Fees Paid in a Cloud Computing Arrangement. The ASU provides guidance to customers about whether a cloud computing arrangement includes a software license. If a cloud computing arrangement includes a software license, then the customer should account for the software license element of the arrangement consistent with the acquisition of other software licenses. If a cloud computing arrangement does not include a software license, the customer should account for the arrangement as a service contract. The ASU does not change the accounting for a customer’s accounting for service contracts. A company can elect to adopt the ASU either prospectively or retrospectively. This guidance is effective for the Company beginning in the first quarter of 2016. Early adoption is permitted. The Company does not expect this guidance to have a material effect on its consolidated financial statements. In April 2015, the FASB issued ASU No. 2015-03, Interest - Imputation of Interest (Subtopic 835-30): Simplifying the Presentation of Debt Issuance Costs. The ASU requires that debt issuance costs related to a recognized debt liability be presented in the balance sheet as a direct deduction from the carrying amount of that debt liability, consistent with debt discounts. The recognition and measurement guidance for debt issuance costs are not affected by this ASU. Early adoption is permitted. This guidance is effective for the Company on a retrospective basis beginning in the first quarter of 2016 and is not expected to have a material effect on the Company's consolidated financial statements. In August 2014, the FASB issued ASU No. 2014-15, Presentation of Financial Statements—Going Concern (Subtopic 205-40): Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern. The new guidance requires management of public and private companies to evaluate whether there is substantial doubt about the entity’s ability to continue as a going concern and, if so, disclose that fact. Management will also be required to evaluate and disclose whether its plans alleviate that doubt. The standard will be effective for the Company's annual period ending December 31, 2016 and interim and annual periods thereafter. Early adoption is permitted. The Company does not expect that the requirement will have an impact on its financial position, results of operations or cash flows. In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606), which requires an entity to recognize the amount of revenue to which it expects to be entitled for the transfer of promised goods or services to customers. The ASU will replace most existing revenue recognition guidance in U.S. GAAP when it becomes effective. The new standard is effective for the Company's annual and interim reporting periods beginning January 1, 2017. Early adoption is not permitted. The standard permits the use of either the retrospective or cumulative effect transition method. The Company is evaluating the effect that ASU 2014-09 will have on its consolidated financial statements and related disclosures. The Company has not yet selected a transition method nor has it determined the effect of the standard on its ongoing financial reporting.

Fair Value Measurements

3 Months Ended

Mar. 31, 2015

Fair Value Disclosures [Abstract]

Fair Value Disclosures

2. Fair Value Measurements

The Company carries short-term investments consisting of marketable securities at fair value on a recurring basis. Fair value is based on the price that would be received from selling an asset in an orderly transaction between market participants at the measurement date. Fair value is estimated by applying the following hierarchy, which prioritizes the inputs used to measure fair value into three levels and bases the categorization within the hierarchy upon the lowest level of input that is available and significant to the fair value measurement:

Level 1 — Observable inputs which include unadjusted quoted prices in active markets for identical assets.

Level 2 — Observable inputs other than Level 1 inputs, such as quoted prices for similar assets, quoted prices for identical or similar assets in inactive markets, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the asset.

Level 3 — Unobservable inputs that are supported by little or no market activity and that are based on management’s assumptions, including fair value measurements determined by using pricing models, discounted cash flow methodologies or similar techniques.

The fair value of assets carried at fair value was determined using the following inputs (in thousands):



	March 31, 2015
	Total		Level 1
Assets
Short-term investments:
U.S. Treasury bills	$	19,999	$	19,999

	December 31, 2014
	Total		Level 1
Assets
Short-term investments:
U.S. Treasury bills	$	20,000	$	20,000

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Short-Term Investments

3 Months Ended

Mar. 31, 2015

Short-term Investments [Abstract]

Short-Term Investments

3. Short-Term Investments

The Company classifies all investments with maturities of three months or less from date of purchase as cash equivalents and all investments with maturities of greater than three months from the date of purchase as short-term investments. The Company classifies its investments in marketable securities as available-for-sale at the time of purchase and as a result, classifies such investments, including securities with maturities beyond twelve months, as current assets in the accompanying condensed consolidated balance sheets.

As of March 31, 2015, short-term investments consisted of the following (in thousands):



	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Aggregate Fair Value
U.S. Treasury bills	$	20,000	$	—	$	(1	)	$	19,999

As of March 31, 2015, the Company's short-term investments will mature in approximately 44 days.

Financial Statement Components

3 Months Ended

Mar. 31, 2015

Financial Statement Components [Abstract]

Financial Statement Components

4. Financial Statement Components

Accounts receivable, net consisted of the following (in thousands):



	March 31, 2015			December 31, 2014
Trade accounts receivable	$	8,000		$	7,482
Unbilled trade accounts receivable, net of advance client deposits	749			918
Allowance for doubtful accounts	(30		)	(65		)
Accounts receivable, net	$	8,719		$	8,335

Property and equipment, net consisted of the following (in thousands):



	March 31, 2015			December 31, 2014
Computer and network equipment	$	25,590		$	24,292
Computer software	2,439			2,264
Furniture and fixtures	1,036			1,030
Leasehold improvements	611			611
Property and equipment	29,676			28,197
Accumulated depreciation and amortization	(17,250		)	(15,626		)
Property and equipment, net	$	12,426		$	12,571

Depreciation and amortization expense associated with property and equipment was $1.6 million and $1.5 million for the three months ended March 31, 2015 and 2014, respectively,

Property and equipment capitalized under capital lease obligations consist primarily of computer and network equipment and were as follows (in thousands):



	March 31, 2015			December 31, 2014
Gross	$	22,328		$	21,025
Less: accumulated depreciation and amortization	(11,983		)	(10,609		)
Total	$	10,345		$	10,416

Accrued and other current liabilities consisted of the following (in thousands):



	March 31, 2015		December 31, 2014
Accrued expenses	$	2,245	$	2,240
Accrued compensation and benefits	5,862		5,078
Accrued and other current liabilities	$	8,107	$	7,318

Restricted Cash

As of March 31, 2015 and December 31, 2014, the Company had $0.2 million and $0.1 million of restricted cash, respectively, under letters of credit primarily related to an insurance policy. As of December 31, 2014, the Company also had restricted cash of $0.7 million related to a letter of credit issued to the Company’s landlord with respect to its lease obligation, which was released in the three months ended March 31, 2015. Restricted cash is included in other assets on the accompanying condensed consolidated balance sheets.

Intangible Assets

3 Months Ended

Mar. 31, 2015

Goodwill and Intangible Assets Disclosure [Abstract]

Intangible Assets Disclosure

5. Intangible Assets

The components of intangible assets, which were acquired in connection with the Company’s acquisition of Face It, Corp., which we refer to as SoCoCare, a social engagement and mobile customer care solution provider, in October 2013, were as follows (in thousands):



	March 31, 2015							December 31, 2014
	Gross Carrying Amount		Accumulated Amortization			Net Carrying Amount		Gross Carrying Amount		Accumulated Amortization			Net Carrying Amount
Developed technology	$	2,460	$	(511	)	$	1,949	$	2,460	$	(423	)	$	2,037
Customer relationships	520		(151		)	369		520		(125		)	395
Domain names	50		(15		)	35		50		(12		)	38
Non-compete agreements	140		(68		)	72		140		(57		)	83
Total	$	3,170	$	(745	)	$	2,425	$	3,170	$	(617	)	$	2,553

Amortization expense related to intangible assets was $0.1 million for each of the three months ended March 31, 2015 and 2014. As of March 31, 2015, the expected future amortization expense for intangible assets was as follows (in thousands):



Period	Expected Future Amortization Expense
Remainder of 2015	$	384
2016	503
2017	465
2018	442
2019	351
2020	280
Total	$	2,425

Long-Term Debt

3 Months Ended

Mar. 31, 2015

Debt Disclosure [Abstract]

Long-Term Debt

6. Long-Term Debt

2013 Loan and Security Agreement

Prior to December 2014, the Company's revolving line of credit was under a loan and security agreement (“2013 Loan and Security Agreement”) with a lender, which was entered into in March 2013 and amended in October 2013 and February 2014.

In December 2014, the Company entered into a third amendment ("Third Amendment") to the 2013 Loan and Security Agreement with the lender to amend this revolving line of credit to, among other things, (a) increase the revolving credit commitment from $12.5 million to $20.0 million, (b) extend the March 2015 maturity date to December 1, 2016 and (c) reduce the interest rate on borrowings by 0.75%, such that the per annum interest rate on outstanding borrowings will be the prime rate plus 0.50%. The Third Amendment also increases the required cash deposit with the bank by $2.0 million to $7.5 million.

The 2013 Loan and Security Agreement is collateralized by substantially all the assets of the Company. Under the terms of the amended revolving line of credit ("Revolving Credit Facility"), the balance outstanding cannot exceed the lesser of (i) $20.0 million or (ii) an amount equal to the Company’s monthly recurring revenue for the three months prior multiplied by the average Dollar-Based Retention Rate over the prior twelve months, less the amount accrued for the Company’s USF obligation (accrued federal fees). As of March 31, 2015, the outstanding principal balance under the Revolving Credit Facility was $12.5 million, which has been disclosed as a non-current liability, and the amount available for additional borrowings was $7.5 million.

In connection with its acquisition of SoCoCare, the Company also borrowed $5.0 million under a term loan (the “Term Loan”) under the 2013 Loan and Security Agreement in October 2013. Monthly interest-only payments were due on the advance at the prime rate plus 1.50% through September 2014. Principal and interest payments are due in equal monthly installments from October 2014 through the maturity of the Term Loan in March 2017. As of March 31, 2015 and December 31, 2014, approximately $4.0 million and $4.5 million, respectively, of this Term Loan was outstanding and is included as notes payable in the condensed consolidated balance sheets. In connection with the Term Loan, the Company issued a warrant to purchase 52,054 shares of its Series D-2 convertible preferred stock at an exercise price of $1.441 per share. The issuance date fair value of this warrant of $0.1 million was recorded as a discount against the debt and is being recognized as additional interest expense over the term of the Term Loan. Upon the effectiveness of the Company’s registration statement filed with the SEC, the conversion of the Company’s preferred stock into common stock and the effectiveness of the 4:1 reverse stock split on April 3, 2014, this warrant became a warrant to purchase 13,013 shares of common stock at an exercise price of $5.76 per share.

The 2013 Loan and Security Agreement contains certain covenants, including the requirement that the Company maintain $7.5 million of cash deposited with the lender for the term of the 2013 Loan and Security Agreement. The Company was in compliance with these covenants as of March 31, 2015. The 2013 Loan and Security Agreement remains senior to other debts, including the debt issued under the 2014 Loan and Security Agreement discussed below.

2014 Loan and Security Agreement

The Company has a term loan facility of $30.0 million with a syndicate of two lenders ("Lenders"), which was entered into in February 2014 and amended in December 2014 and February 2015 (the “2014 Loan and Security Agreement”). The term loan facility is available to the Company in tranches; the first tranche for $20.0 million was advanced upon the closing of the agreement and the remaining $10.0 million is available for drawdown by the Company until February 2016 in $1.0 million increments. The Company incurred $0.4 million in debt issuance costs in connection with borrowing the first tranche in February 2014. The term loan bears interest at a variable per annum rate equal to the greater of 10% or LIBOR plus 9%. Interest is due and payable on the last business day of each month during the term of the loan commencing in February 2014. Monthly principal payments are due beginning in February 2016 based on 1/60th of the outstanding balance at that time and will continue until all remaining principal outstanding under the term loan becomes due and payable in February 2019. All amounts outstanding under this loan facility have been disclosed as part of 'Notes payable - less current portion' in the condensed consolidated balance sheet as of March 31, 2015.

The term loan is secured by substantially all the assets of the Company and is subordinate to the 2013 Loan and Security Agreement. The 2014 Loan and Security Agreement contains certain covenants and includes the occurrence of a material adverse event, as defined in the agreement and determined by the Lenders, as an event of default. As of March 31, 2015, the Company was in compliance with these covenants.

In connection with entering into the 2014 Loan and Security Agreement, the Company issued to the Lenders warrants to purchase 177,865 shares of common stock at $10.12 per share, which vest and become exercisable over a ten year term from the date of issuance, based on amounts drawn under the $30.0 million term loan facility. The exercise price of such warrants was subject to adjustment in the event of issuances of common stock by the Company at a price lower than the exercise price of such warrants any time prior to the date of effectiveness of the Company’s initial public offering ("IPO") and other corporate actions. Therefore, upon issuance the warrants were classified as a liability to the Company, which has been reclassified to additional paid-in capital upon the Company's IPO at which time these warrants were indexed to the Company's common stock. Based on the drawdown of $20.0 million in February 2014, 118,577 shares of common stock issuable under the warrants vested and are exercisable by the Lenders. The fair value of the vested warrants of $1.0 million was recorded as a discount against the debt proceeds and is being recognized as additional interest expense over the term of the loan. As of March 31, 2015, 59,288 shares of common stock issuable under the warrants pertaining to the undrawn $10.0 million remain unvested.

Promissory Note

In July 2013, the Company issued a promissory note to the Universal Service Administrative Company ("USAC") for $4.1 million as a financing arrangement for that amount of accrued federal fees. The promissory note carries a fixed annual interest rate of 12.75% and is repayable in 42 equal monthly installments of principal and interest beginning in August 2013. As of March 31, 2015 and December 31, 2014, approximately $2.4 million and $2.6 million, respectively, of this promissory note was outstanding and is included as notes payable in the accompanying condensed consolidated balance sheets.

As of March 31, 2015 and December 31, 2014, the Company’s outstanding debt is summarized as follows (in thousands):



	March 31, 2015			December 31, 2014
Term loan under 2014 Loan and Security Agreement	$	20,000		$	20,000
Term loan under 2013 Loan and Security Agreement	4,000			4,500
Promissory note to USAC	2,358			2,640
Revolving line of credit, non-current	12,500			12,500
Total debt	38,858			39,640
Less: discount	(1,132		)	(1,216		)
Total debt, net carrying value	$	37,726		$	38,424
Less: current portion of debt	(3,528		)	(3,146		)
Total debt, less current portion	34,198			35,278

Maturities of the Company’s outstanding debt as of March 31, 2015 are as follows (in thousands):



Period	Amount to Mature
Remainder of 2015	$	2,398
2016	19,507
2017	4,620
2018	4,000
2019	8,333
Total	$	38,858

Stockholders' Equity

3 Months Ended

Mar. 31, 2015

Equity [Abstract]

Stockholders' Equity

7. Stockholders’ Equity

Capital Structure

The Company is authorized to issue 450,000,000 shares of common stock with a par value of $0.001 per share. As of March 31, 2015, the Company had 49,611,533 shares of common stock issued and outstanding.

The Company is also authorized to designate and issue up to 5,000,000 shares of preferred stock with a par value of $0.001 per share in one or more series without stockholder approval and to fix the rights, preferences, privileges and restrictions thereof. As of March 31, 2015, the Company had no shares of preferred stock issued and outstanding.

Common Stock Subject to Forfeiture

In connection with employment and service agreements entered into in connection with the Company’s acquisition of SoCoCare in October 2013 ("Acquisition Date"), the Company issued 118,577 shares of unvested restricted common stock, the vesting of which is contingent upon continuing employment or services and subject to forfeiture. During October 2014, 50% of such shares vested. During the three months ended March 31, 2015, in accordance with the applicable stock issuance agreement, the vesting on 37,905 shares accelerated in connection with the termination of employment of a shareholder. The remaining 21,384 shares will vest on the second anniversary of the Acquisition Date, provided the recipients thereof continue in service to the Company through such date. These shares were valued at $8.48 per share, based on the Acquisition Date fair value of the Company’s common stock. This amount is being recorded as stock-based compensation on a straight-line basis over the requisite service periods. For each of the three months ended March 31, 2015 and 2014, $0.2 million was included as stock-based compensation expense related to these shares. As of March 31, 2015 and December 31, 2014, the 21,384 shares and 59,289 shares that were subject to forfeiture were included in issued and outstanding shares of common stock, respectively.

Warrants

As of March 31, 2015 and December 31, 2014, the Company had outstanding warrants to purchase 359,596 shares of common stock with a weighted-average exercise price of $5.59 per share, which expire on various dates between February 2020 and February 2024.

Common Stock Reserved for Future Issuance

Shares of common stock reserved for future issuance related to outstanding equity awards, common stock warrants, and employee equity incentive plans were as follows (in thousands):



		March 31, 2015
Stock options outstanding		6,891
Restricted stock units outstanding		1,458
Shares available for future grant under 2014 Plan		5,756
Shares available for future issuance under ESPP		1,217
Common stock warrants outstanding		360
Total shares of common stock reserved		15,682

Equity Incentive Plans

Prior to the IPO, the Company granted stock options under its Amended and Restated 2004 Equity Incentive Plan, as amended (the “2004 Plan”).

In March 2014, the Company’s board of directors and stockholders approved the 2014 Equity Incentive Plan (“2014 Plan”) and 5,300,000 shares of common stock were reserved for issuance under the 2014 Plan. In addition, on the first day of each year beginning in 2015 and ending in 2024, the 2014 Plan provides for an annual automatic increase to the shares reserved for issuance in an amount equal to 5% of the total number of shares outstanding on December 31st of the preceding calendar year or a lesser number as determined by the Company’s board of directors. Pursuant to the automatic annual increase, 2,466,124 additional shares were reserved under the 2014 Plan on January 1, 2015.

Upon the effectiveness of the 2014 Plan on April 3, 2014, no future grants will be made under the 2004 Plan. All shares reserved under the 2004 Plan became available for grant under the 2014 Plan. Any forfeited or expired shares that would otherwise return to the 2004 Plan after the IPO instead return to the 2014 Plan. As of March 31, 2015, 5,756,262 shares of common stock were available for future grant under the 2014 Plan.

The 2004 Plan and the 2014 Plan are described in the Company’s Annual Report on Form 10-K for the year ended December 31, 2014.

Stock Options

A summary of the Company’s stock option activities during the three months ended March 31, 2015 is as follows (in thousands, except years and per share data):



	Number of Shares Outstanding		Weighted Average Exercise Price		Weighted Average Remaining Contractual Life (Years)	Aggregate Intrinsic Value
Outstanding as of December 31, 2014	7,164		$	4.34
Options granted	—		—
Options exercised	(209	)	0.55
Options forfeited or expired	(64	)	6.35
Outstanding as of March 31, 2015	6,891		$	4.44	7.2	$	15,714

The Company has computed the aggregate intrinsic value amounts disclosed in the above table based on the difference between the original exercise price of the options and the fair market value of the Company’s common stock of $5.56 as of March 31, 2015 for all in-the-money options outstanding.

Restricted Stock Units

A summary of the Company's RSU activities during the three months ended March 31, 2015 is as follows (in thousands, except per share data):



	Number of Shares		Weighted Average Grant Date Fair Value Per Share
Outstanding as of December 31, 2014	1,370		$	5.21
RSUs granted	188		4.56
RSUs vested and released	(79	)	5.31
RSUs forfeited	(21	)	4.99
Outstanding as of March 31, 2015	1,458		$	5.13

Employee Stock Purchase Plan

The Company's 2014 Employee Stock Purchase Plan ("ESPP") became effective on April 3, 2014 and is described in the Company’s Annual Report on Form 10-K for the year ended December 31, 2014. The number of shares of common stock originally reserved for issuance under the ESPP was 880,000 shares, which will increase automatically each year, beginning on January 1, 2015 and continuing through January 1, 2024, by the lesser of (i) 1% of the total number of shares of the Company’s common stock outstanding on December 31 of the preceding calendar year; (ii) 1,000,000 shares of common stock (subject to adjustment to reflect any split or combination of the Company’s common stock); or (iii) such lesser number as determined by the Company’s board of directors. Pursuant to the automatic annual increase, 493,224 additional shares were reserved under the ESPP on January 1, 2015. As of March 31, 2015, 1,217,093 shares of common stock were available for future grants under the ESPP.

During the three months ended March 31, 2015, no purchases were made under the ESPP.

Stock-Based Compensation

Stock-based compensation expenses for the three months ended March 31, 2015 and 2014 are as follows (in thousands):



	Three Months Ended
	March 31, 2015		March 31, 2014
Cost of revenue	$	188	$	87
Research and development	574		350
Sales and marketing	524		326
General and administrative	949		433
Total stock-based compensation	$	2,235	$	1,196

As of March 31, 2015, unrecognized stock-based compensation expenses by award type, net of estimated forfeitures, and their expected weighted-average recognition periods are summarized in the following table (in thousands, except years).



	Stock Option		RSU		ESPP
Unrecognized stock-based compensation expense	$	9,710	$	5,280	$	131
Weighted-average amortization period	2.7 years		3.4 years		0.1 years

The Company recognizes stock-based compensation expense that is calculated based upon awards ultimately expected to vest and, thus, stock-based compensation expense is reduced for estimated forfeitures. Forfeitures are estimated at the time of grant and revised, if necessary, in subsequent periods if actual forfeitures differ from those estimates. All stock-based compensation for equity awards granted to employees and non-employee directors is measured based on the grant date fair value of the award.

The Company values RSUs at the closing market price of its common stock on the date of grant. The Company estimates the fair value of each stock option and purchase right under the ESPP granted to employees on the date of grant using the Black-Scholes option-pricing model and using the assumptions noted in the below table. The weighted-average assumptions used to value stock options granted during the three months ended March 31, 2015 and 2014 were as follows:



Stock Options	Three Months Ended
	March 31, 2015	March 31, 2014
Expected term (years)	*	6.1
Volatility	*	56%
Risk-free interest rate	*	1.8%
Dividend yield	*	—


* No stock options were granted during the three months ended March 31, 2015.

Net Loss Per Share

3 Months Ended

Mar. 31, 2015

Earnings Per Share [Abstract]

Net Loss Per Share

8. Net Loss Per Share

Basic net loss per share is calculated by dividing net loss by the weighted average number of common shares outstanding during the period, and excludes any dilutive effects of employee stock-based awards and warrants. Diluted net income per share is computed giving effect to all potentially dilutive common shares, including common stock issuable upon exercise of stock options and warrants and vesting of restricted stock. As the Company had net losses for the three months ended March 31, 2015 and 2014, all potentially issuable common shares were determined to be anti-dilutive.

The following table presents the calculation of basic and diluted net loss per share (in thousands, except per share data).



	Three Months Ended
	March 31, 2015			March 31, 2014
Net loss	$	(8,903	)	$	(8,320	)
Weighted-average shares used in computing basic and diluted net loss per share	49,433			5,608
Basic and diluted net loss per share	$	(0.18	)	$	(1.48	)

The following securities were excluded from the calculation of diluted net loss per share attributable to common stockholders because their effect would have been anti-dilutive for the periods presented (in thousands).



	March 31, 2015	March 31, 2014
Convertible preferred stock	—	30,595
Stock options	6,891	7,345
Restricted stock units	1,458	—
ESPP	171	—
Common stock warrants	360	—
Convertible preferred stock warrants	—	525
Common stock subject to repurchase or forfeiture	21	141
Total	8,901	38,606

Income Taxes	3 Months Ended
Income Taxes	Mar. 31, 2015
Income Tax Disclosure [Abstract]
Income Tax Disclosure	9. Income Taxes The provision for income taxes for the three months ended March 31, 2015 and 2014 was approximately $18 thousand and $27 thousand, respectively. The provision for income taxes consisted primarily of foreign income taxes. For the three months ended March 31, 2015 and 2014, the provision for income taxes differed from the statutory amount primarily due to state and foreign taxes currently payable, and the Company realized no benefit for current year losses due to maintaining a full valuation allowance against its domestic and foreign net deferred tax assets. The realization of tax benefits of deferred tax assets is dependent upon future levels of taxable income, of an appropriate character, in the periods the items are expected to be deductible or taxable. Based on the available objective evidence, the Company does not believe it is more likely than not that the net deferred tax assets will be realizable. Accordingly, the Company has provided a full valuation allowance against the domestic and foreign net deferred tax assets as of March 31, 2015 and December 31, 2014. The Company intends to maintain the remaining valuation allowance until sufficient positive evidence exists to support a reversal of, or decrease in, the valuation allowance. During the three months ended March 31, 2015, there were no material changes to the total amount of unrecognized tax benefits.

Commitments and Contingencies	3 Months Ended
Commitments and Contingencies	Mar. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies Disclosure	10. Commitments and Contingencies Commitments The Company’s principal commitments consist of obligations under operating lease agreements for offices, research and development, and sales and marketing facilities, and agreements with third parties to provide co-location hosting and telecommunication usage services. These commitments as of December 31, 2014 are disclosed in the Company's Annual Report on Form 10-K for the year ended December 31, 2014, and did not change during the three months ended March 31, 2015 except for the acquisition of certain additional data center and network equipment and software under multiple capital leases. As of March 31, 2015, total minimum future payment commitments under these capital leases were approximately $1.7 million, of which $0.4 million is due in 2015, with the remainder due over approximately 2.3 years thereafter. Universal Services Fund Liability During the third quarter of 2012, the Company determined that based on its business activities, it is classified as a telecommunications service provider for regulatory purposes and it should make direct contributions to the federal Universal Service Fund and related funds ("USF") based on revenues it receives from the resale of interstate and international telecommunications services. Previously, the Company had believed that the telecommunications services were an integral part of an information service that the Company provides via its software and had instead made indirect USF contributions via payments to its wholesale telecommunications service providers. In order to comply with the obligation to make direct contributions, the Company has made a voluntary self-disclosure to the Federal Communications Commission (“FCC”) Enforcement Bureau and has registered with the USAC, which is charged by the FCC with administering the USF. The Company has filed exemption certificates with its wholesale telecommunications service providers in order to eliminate its obligation to reimburse such wholesale telecommunications service providers for their USF contributions calculated on services sold to the Company. The Company’s registration with USAC subjects it to assessments for unpaid USF contributions, as well as interest thereon and civil penalties, due to its late registration and past failure to recognize its obligation as a USF contributor and as an international carrier. The Company will be required to pay assessments for periods prior to the Company’s registration. While the Company is in administrative proceedings before the FCC to limit such back assessments to the period 2008 through 2012, it is possible that it will be required to pay back assessments for the period from 2003 through 2007. The Company will also face a regulatory and contractual challenge in seeking recovery or credit for its USF reimbursement payments previously made to its wholesale telecommunications service providers of up to $3.1 million as of March 31, 2015 and December 31, 2014. In 2013, the Company began remitting required contributions on a prospective basis directly to USAC. In July 2013, the Company and USAC agreed to a financing arrangement for the undisputed portion of the unpaid USF contributions and related interest for the periods 2008 through 2012 whereby the Company issued to USAC a promissory note payable in the amount of $4.1 million. The repayment terms of the promissory note payable are disclosed in Note 6. As of March 31, 2015, the balance of the promissory note payable was $2.4 million and is included in the notes payable amounts on the condensed consolidated balance sheets. In addition to the promissory note payable, the Company had an accrued liability for the unpaid USF contributions and related interest and penalties of $5.5 million and $5.2 million included in accrued federal fees on the condensed consolidated balance sheets as of March 31, 2015 and December 31, 2014, respectively, of which $0.8 million pertains to periods prior to 2008. For each of the three months ended March 31, 2015 and 2014, the Company recorded interest and penalty expenses of $0.1 million as a charge to general and administrative expense, which were related to its unpaid USF obligations for the periods prior to 2013. No amounts related to the potential recovery or credit of USF contributions paid by the Company to its wholesale telecommunications service providers were recognized in the accompanying condensed consolidated financial statements. In connection with the Company's late registration with the USAC and past failure to recognize its obligation as a USF contributor and as an international carrier, in October 2014, the FCC Enforcement Bureau began to negotiate with the Company a consent decree and a civil penalty to conclude its investigation into the Company's 2008 - 2012 USF contribution and international carrier authorization compliance. On October 28, 2014, the FCC Enforcement Bureau and the Company tentatively agreed on a $2.0 million civil penalty and are negotiating a consent decree to resolve this matter. Principal payments of the civil penalty will likely be payable to the U.S. Treasury over 36 months beginning on the date of execution, which the Company anticipates will be in the course of 2015, under an installment payment plan to be further negotiated by the Company and the FCC Enforcement Bureau. Based on the information that became available in October 2014, the Company believed that this probable loss existed and became reasonably estimable and therefore accrued a liability of $2.0 million within 'Accrued federal fees' in the condensed consolidated balance sheet in the third quarter of 2014, which was charged to general and administrative expense. There were no changes in this accrued probable loss as of March 31, 2015. State and Local Taxes and Surcharges During 2013, the Company analyzed its activities and determined it may be obligated to collect and remit various state and local taxes and surcharges on its usage-based fees. The Company had not remitted state and local taxes on usage-based fees in any of the periods prior to 2014 and therefore accrued a sales tax liability for this contingency. In January 2014, the Company commenced paying such taxes and surcharges to certain state authorities. In June 2014, the Company commenced collecting state and local taxes or surcharges on usage-based fees from its clients on a current basis and remitting such taxes to the applicable state taxing authorities. During the three months ended March 31, 2015 and 2014, the Company has remitted $27 thousand and $0.1 million, respectively, for its state and local taxes on usage-based fees related to the periods prior to June 2014. For the three months ended March 31, 2015 and 2014, the Company recognized general and administrative expense of $0.1 million and $0.5 million, respectively, related to its estimated sales tax liability on usage-based fees, which was not being collected from its clients. The Company’s estimate of the probable loss incurred under this contingency is based on its analysis of the source location of its usage-based fees and the regulations and rules in each state. In April 2012, the Company commenced collecting and remitting sales taxes on sales of subscription services in all states in which it determined it was obligated to do so. During the first quarter of 2015, the Company conducted an updated sales tax review of the taxability of sales of its subscription services. As a result, the Company determined that it may be obligated to collect and remit sales taxes on such sales in four additional states. Based on its best estimate of the probable sales tax liability in those four states relating to its sales of subscription services during the period 2011 through 2014, for the three months ended March 31, 2015, the Company recorded a general and administrative expense of $0.6 million as an out of period adjustment to accrue for such taxes. The accrued tax liability was included in "Sales tax liability" on the condensed consolidated balance sheets. During 2015, the Company expects to commence collecting such state sales taxes from its clients on a current basis and remitting such taxes to the applicable state taxing authorities. As of March 31, 2015, the Company had total accrued liabilities of $3.3 million for its contingent state and local sales taxes and surcharges that were not being collected from its clients but may be imposed by various states and municipalities, of which $1.0 million and $2.3 million was included in current and non-current "Sales tax liability" on the condensed consolidated balance sheets, respectively. As of December 31, 2014, the Company had total accrued liabilities of $2.6 million for such contingent state and local sales taxes and surcharges, which was included in non-current "Sales tax liability" on the condensed consolidated balance sheets. Legal Matters The Company is involved in various legal and regulatory matters arising in the normal course of business. In management’s opinion, resolution of these matters is not expected to have a material impact on the Company’s consolidated results of operations, cash flows, or its financial position. However, depending on the nature and timing of any such dispute, an unfavorable resolution of a matter could materially affect the Company’s future consolidated results of operations, cash flows or financial position in a particular period. The Company is currently involved in the following lawsuits as a defendant. NobelBiz Litigation In April 2012, NobelBiz, Inc., a telecommunication solutions company, brought a patent infringement lawsuit in the U.S. District Court for the Eastern District of Texas against the Company seeking a permanent injunction, damages and attorneys' fees. The Company responded to the complaint and preliminary injunction request by asserting non-infringement and invalidity of the patent. In March 2013, the court granted the Company's motion to transfer the case to the U.S. District Court for the Northern District of California subsequent to which the complainant amended its claim to include another related patent. The Company has responded to this amended claim by continuing to assert non-infringement and invalidity of the patents. During December 2013, the court in California held a status conference and subsequently held a claim construction hearing regarding the patents on August 22, 2014. On January 16, 2015, the court issued an order regarding claim construction of the two patents-in-suit, and on April 6, 2015, the court held a case management conference setting further dates in the case. The court set a trial date of June 20, 2016, and set February 16, 2016 as the deadline to file motions for summary judgment. The Company has investigated the claims alleged in the complaint and believes that it has good defenses to the claims. Accordingly, the Company has not accrued a loss related to this matter as the Company does not believe that it is probable that a loss will be incurred. UHC Claim On January 29, 2015, Soneet Kapila, the Chapter 11 Trustee for the estate of Universal Health Care Group, Inc., which entity serves as the sole member of American Managed Care, LLC (“AMC”), filed an adversary complaint against the Company in the United States Bankruptcy Court for the Middle District of Florida. The adversary proceeding, Soneet Kapila v. Five9, Inc., Case No. 13-05952 (KRM), Adv. No. 15-00092 (KRM), sought to avoid and recover as preferential payments, actual fraudulent transfers and/or constructive fraudulent transfers certain payments that the Company allegedly received from AMC in return for services provided by the Company between May 3, 2011 and May 3, 2014. The trustee sought approximately $2.5 million in damages. The matter has been settled, with Bankruptcy Court approval, for a cash payment by the Company of $99,000, which has been accrued by the Company with a charge to general and administrative expense during the three months ended March 31, 2015. The accrued liability was included in "Accrued and other current liabilities" on the condensed consolidated balance sheets. The Company recognizes general and administrative expense for legal fees in the period the services are provided. Indemnification Agreements In the ordinary course of business, the Company indemnifies various clients, vendors, lessors, business partners and other parties with respect to certain matters, including, but not limited to, losses arising out of breach of such agreements, services to be provided by the Company or from intellectual property infringement claims made by third parties. In addition, the Company has entered into indemnification agreements with its directors, officers and certain employees that require the Company, among other things, to indemnify them against certain liabilities that may arise by reason of their status or service as directors, officers or employees. No demands have been made upon the Company to provide indemnification under such agreements and thus there are no claims that the Company is aware of that would have a material effect on the Company’s condensed consolidated balance sheets, condensed consolidated statements of operations and comprehensive loss, or condensed consolidated statements of cash flows.

Geographical Information

3 Months Ended

Mar. 31, 2015

Segment Reporting [Abstract]

Geographical Information

11. Geographical Information

The following table is a summary of revenues by geographic region based on client billing address and has been estimated based on the amounts billed to clients during the periods (in thousands).



	Three Months Ended
	March 31, 2015		March 31, 2014
United States	$	28,279	$	22,434
International	1,995		1,840
Total revenue	$	30,274	$	24,274

The following table summarizes total property and equipment, net in the respective locations (in thousands).



	March 31, 2015		December 31, 2014
United States	$	10,415	$	10,625
International	2,011		1,946
Property and equipment, net	$	12,426	$	12,571

- Definition

The entire disclosure for reporting segments including data and tables. Reportable segments include those that meet any of the following quantitative thresholds a) it's reported revenue, including sales to external customers and intersegment sales or transfers is 10 percent or more of the combined revenue, internal and external, of all operating segments b) the absolute amount of its reported profit or loss is 10 percent or more of the greater, in absolute amount of 1) the combined reported profit of all operating segments that did not report a loss or 2) the combined reported loss of all operating segments that did report a loss c) its assets are 10 percent or more of the combined assets of all operating segments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 34
-URI http://asc.fasb.org/extlink&oid=6534315&loc=d3e8981-108599

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 41
-URI http://asc.fasb.org/extlink&oid=6534315&loc=d3e9038-108599

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 4: http://www.xbrl.org/2003/role/presentationRef
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-URI http://asc.fasb.org/extlink&oid=6534315&loc=d3e8595-108599

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6534315&loc=d3e8380-108599

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-URI http://asc.fasb.org/extlink&oid=6534315&loc=d3e8933-108599

Reference 7: http://www.xbrl.org/2003/role/presentationRef
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-Topic 280
-SubTopic 10
-Section 50
-Paragraph 26
-URI http://asc.fasb.org/extlink&oid=6534315&loc=d3e8844-108599

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 35
-URI http://asc.fasb.org/extlink&oid=6534315&loc=d3e8984-108599

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 40
-URI http://asc.fasb.org/extlink&oid=6534315&loc=d3e9031-108599

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 42
-URI http://asc.fasb.org/extlink&oid=6534315&loc=d3e9054-108599

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
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Reference 12: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
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-URI http://asc.fasb.org/extlink&oid=6534315&loc=d3e8864-108599

Reference 13: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
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-URI http://asc.fasb.org/extlink&oid=6534315&loc=d3e8924-108599

Reference 14: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
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-URI http://asc.fasb.org/extlink&oid=6534315&loc=d3e8906-108599

+ Details

Description of Business and Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation The accompanying condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States (“GAAP”) and applicable rules and regulations of the Securities and Exchange Commission (“SEC”) regarding interim financial reporting. Certain information and note disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. Therefore, these condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and notes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2014. All intercompany transactions and balances have been eliminated in consolidation.
Use of Estimates	Use of Estimates The preparation of consolidated financial statements in accordance with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenue and expenses during the reporting period. The significant estimates made by management affect revenue, the allowance for doubtful accounts, intangible assets, including goodwill, loss contingencies, including the Company’s accrual for federal fees and sales tax liability, accrued liabilities, stock-based compensation, fair value calculations of the convertible preferred and common stock warrant liabilities, provision for income taxes and uncertain tax positions. Management periodically evaluates such estimates and they are adjusted prospectively based upon such periodic evaluation. Actual results could differ from those estimates.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In April 2015, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") No. 2015-05, Intangibles - Goodwill and Other - Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Fees Paid in a Cloud Computing Arrangement. The ASU provides guidance to customers about whether a cloud computing arrangement includes a software license. If a cloud computing arrangement includes a software license, then the customer should account for the software license element of the arrangement consistent with the acquisition of other software licenses. If a cloud computing arrangement does not include a software license, the customer should account for the arrangement as a service contract. The ASU does not change the accounting for a customer’s accounting for service contracts. A company can elect to adopt the ASU either prospectively or retrospectively. This guidance is effective for the Company beginning in the first quarter of 2016. Early adoption is permitted. The Company does not expect this guidance to have a material effect on its consolidated financial statements. In April 2015, the FASB issued ASU No. 2015-03, Interest - Imputation of Interest (Subtopic 835-30): Simplifying the Presentation of Debt Issuance Costs. The ASU requires that debt issuance costs related to a recognized debt liability be presented in the balance sheet as a direct deduction from the carrying amount of that debt liability, consistent with debt discounts. The recognition and measurement guidance for debt issuance costs are not affected by this ASU. Early adoption is permitted. This guidance is effective for the Company on a retrospective basis beginning in the first quarter of 2016 and is not expected to have a material effect on the Company's consolidated financial statements. In August 2014, the FASB issued ASU No. 2014-15, Presentation of Financial Statements—Going Concern (Subtopic 205-40): Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern. The new guidance requires management of public and private companies to evaluate whether there is substantial doubt about the entity’s ability to continue as a going concern and, if so, disclose that fact. Management will also be required to evaluate and disclose whether its plans alleviate that doubt. The standard will be effective for the Company's annual period ending December 31, 2016 and interim and annual periods thereafter. Early adoption is permitted. The Company does not expect that the requirement will have an impact on its financial position, results of operations or cash flows. In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606), which requires an entity to recognize the amount of revenue to which it expects to be entitled for the transfer of promised goods or services to customers. The ASU will replace most existing revenue recognition guidance in U.S. GAAP when it becomes effective. The new standard is effective for the Company's annual and interim reporting periods beginning January 1, 2017. Early adoption is not permitted. The standard permits the use of either the retrospective or cumulative effect transition method. The Company is evaluating the effect that ASU 2014-09 will have on its consolidated financial statements and related disclosures. The Company has not yet selected a transition method nor has it determined the effect of the standard on its ongoing financial reporting.

Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2015

Fair Value Disclosures [Abstract]

Schedule of Assets and Liabilities Carried at Fair Value

The fair value of assets carried at fair value was determined using the following inputs (in thousands):



	March 31, 2015
	Total		Level 1
Assets
Short-term investments:
U.S. Treasury bills	$	19,999	$	19,999

	December 31, 2014
	Total		Level 1
Assets
Short-term investments:
U.S. Treasury bills	$	20,000	$	20,000

Short-Term Investments (Tables)

3 Months Ended

Mar. 31, 2015

Short-term Investments [Abstract]

Schedule of Short-Term Investments

As of March 31, 2015, short-term investments consisted of the following (in thousands):



	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Aggregate Fair Value
U.S. Treasury bills	$	20,000	$	—	$	(1	)	$	19,999

- Definition

Tabular disclosure of available-for-sale securities which includes, but is not limited to, changes in the cost basis and fair value, fair value and gross unrealized gain (loss), fair values by type of security, contractual maturity and classification, amortized cost basis, contracts to acquire securities to be accounted for as available-for-sale, debt maturities, transfers to trading, change in net unrealized holding gain (loss) net of tax, continuous unrealized loss position fair value, aggregate losses qualitative disclosures, other than temporary impairment (OTTI) losses or other disclosures related to available for sale securities.

+ References + Details

Financial Statement Components (Tables)

3 Months Ended

Mar. 31, 2015

Financial Statement Components [Abstract]

Schedule of Accounts Receivable

Accounts receivable, net consisted of the following (in thousands):



	March 31, 2015			December 31, 2014
Trade accounts receivable	$	8,000		$	7,482
Unbilled trade accounts receivable, net of advance client deposits	749			918
Allowance for doubtful accounts	(30		)	(65		)
Accounts receivable, net	$	8,719		$	8,335

Schedule of Property and Equipment

Property and equipment, net consisted of the following (in thousands):



	March 31, 2015			December 31, 2014
Computer and network equipment	$	25,590		$	24,292
Computer software	2,439			2,264
Furniture and fixtures	1,036			1,030
Leasehold improvements	611			611
Property and equipment	29,676			28,197
Accumulated depreciation and amortization	(17,250		)	(15,626		)
Property and equipment, net	$	12,426		$	12,571

Schedule of Capital Leased Property and Equipment

Property and equipment capitalized under capital lease obligations consist primarily of computer and network equipment and were as follows (in thousands):



	March 31, 2015			December 31, 2014
Gross	$	22,328		$	21,025
Less: accumulated depreciation and amortization	(11,983		)	(10,609		)
Total	$	10,345		$	10,416

Schedule of Accrued and Other Current Liabilities

Accrued and other current liabilities consisted of the following (in thousands):



	March 31, 2015		December 31, 2014
Accrued expenses	$	2,245	$	2,240
Accrued compensation and benefits	5,862		5,078
Accrued and other current liabilities	$	8,107	$	7,318

Intangible Assets (Tables)

3 Months Ended

Mar. 31, 2015

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of Intangible Assets



	March 31, 2015							December 31, 2014
	Gross Carrying Amount		Accumulated Amortization			Net Carrying Amount		Gross Carrying Amount		Accumulated Amortization			Net Carrying Amount
Developed technology	$	2,460	$	(511	)	$	1,949	$	2,460	$	(423	)	$	2,037
Customer relationships	520		(151		)	369		520		(125		)	395
Domain names	50		(15		)	35		50		(12		)	38
Non-compete agreements	140		(68		)	72		140		(57		)	83
Total	$	3,170	$	(745	)	$	2,425	$	3,170	$	(617	)	$	2,553

Schedule of Expected Future Amortization Expense of Intangible Assets

As of March 31, 2015, the expected future amortization expense for intangible assets was as follows (in thousands):



Period	Expected Future Amortization Expense
Remainder of 2015	$	384
2016	503
2017	465
2018	442
2019	351
2020	280
Total	$	2,425

Long-Term Debt (Tables)

3 Months Ended

Mar. 31, 2015

Debt Disclosure [Abstract]

Schedule of Debt

As of March 31, 2015 and December 31, 2014, the Company’s outstanding debt is summarized as follows (in thousands):



	March 31, 2015			December 31, 2014
Term loan under 2014 Loan and Security Agreement	$	20,000		$	20,000
Term loan under 2013 Loan and Security Agreement	4,000			4,500
Promissory note to USAC	2,358			2,640
Revolving line of credit, non-current	12,500			12,500
Total debt	38,858			39,640
Less: discount	(1,132		)	(1,216		)
Total debt, net carrying value	$	37,726		$	38,424
Less: current portion of debt	(3,528		)	(3,146		)
Total debt, less current portion	34,198			35,278

Schedule of Maturities of Debt

Maturities of the Company’s outstanding debt as of March 31, 2015 are as follows (in thousands):



Period	Amount to Mature
Remainder of 2015	$	2,398
2016	19,507
2017	4,620
2018	4,000
2019	8,333
Total	$	38,858

- Definition

Tabular disclosure of long-debt instruments or arrangements, including identification, terms, features, collateral requirements and other information necessary to a fair presentation. These are debt arrangements that originally required repayment more than twelve months after issuance or greater than the normal operating cycle of the entity, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21475-112644

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6479336&loc=d3e64711-112823

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(e),(f))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=34725769&loc=d3e28878-108400

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21538-112644

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21506-112644

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28541-108399

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399

Reference 10: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21521-112644

Reference 11: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 22
-Article 5

+ Details

Stockholders' Equity (Tables)

3 Months Ended

Mar. 31, 2015

Equity [Abstract]

Schedule of Common Stock Reserved for Future Issuance

Shares of common stock reserved for future issuance related to outstanding equity awards, common stock warrants, and employee equity incentive plans were as follows (in thousands):



		March 31, 2015
Stock options outstanding		6,891
Restricted stock units outstanding		1,458
Shares available for future grant under 2014 Plan		5,756
Shares available for future issuance under ESPP		1,217
Common stock warrants outstanding		360
Total shares of common stock reserved		15,682

Schedule of Stock Option Activities

A summary of the Company’s stock option activities during the three months ended March 31, 2015 is as follows (in thousands, except years and per share data):



	Number of Shares Outstanding		Weighted Average Exercise Price		Weighted Average Remaining Contractual Life (Years)	Aggregate Intrinsic Value
Outstanding as of December 31, 2014	7,164		$	4.34
Options granted	—		—
Options exercised	(209	)	0.55
Options forfeited or expired	(64	)	6.35
Outstanding as of March 31, 2015	6,891		$	4.44	7.2	$	15,714

Schedule of RSU Activities

A summary of the Company's RSU activities during the three months ended March 31, 2015 is as follows (in thousands, except per share data):



	Number of Shares		Weighted Average Grant Date Fair Value Per Share
Outstanding as of December 31, 2014	1,370		$	5.21
RSUs granted	188		4.56
RSUs vested and released	(79	)	5.31
RSUs forfeited	(21	)	4.99
Outstanding as of March 31, 2015	1,458		$	5.13

Schedule of Stock-based Compensation Expense

Stock-based compensation expenses for the three months ended March 31, 2015 and 2014 are as follows (in thousands):



	Three Months Ended
	March 31, 2015		March 31, 2014
Cost of revenue	$	188	$	87
Research and development	574		350
Sales and marketing	524		326
General and administrative	949		433
Total stock-based compensation	$	2,235	$	1,196



	Stock Option		RSU		ESPP
Unrecognized stock-based compensation expense	$	9,710	$	5,280	$	131
Weighted-average amortization period	2.7 years		3.4 years		0.1 years

Schedule of Weighted-Average Valuation Assumptions, Stock Option

The weighted-average assumptions used to value stock options granted during the three months ended March 31, 2015 and 2014 were as follows:



Stock Options	Three Months Ended
	March 31, 2015	March 31, 2014
Expected term (years)	*	6.1
Volatility	*	56%
Risk-free interest rate	*	1.8%
Dividend yield	*	—


* No stock options were granted during the three months ended March 31, 2015.

Net Loss Per Share (Tables)

3 Months Ended

Mar. 31, 2015

Earnings Per Share [Abstract]

Basic and Diluted Net Loss Per Share

The following table presents the calculation of basic and diluted net loss per share (in thousands, except per share data).



	Three Months Ended
	March 31, 2015			March 31, 2014
Net loss	$	(8,903	)	$	(8,320	)
Weighted-average shares used in computing basic and diluted net loss per share	49,433			5,608
Basic and diluted net loss per share	$	(0.18	)	$	(1.48	)

Schedule of Antidilutive Securities Excluded from Computation of Net Loss Per Share



	March 31, 2015	March 31, 2014
Convertible preferred stock	—	30,595
Stock options	6,891	7,345
Restricted stock units	1,458	—
ESPP	171	—
Common stock warrants	360	—
Convertible preferred stock warrants	—	525
Common stock subject to repurchase or forfeiture	21	141
Total	8,901	38,606

Geographical Information (Tables)

3 Months Ended

Mar. 31, 2015

Segment Reporting [Abstract]

Schedule of Revenues and Property and Equipment by Geographic Region

The following table is a summary of revenues by geographic region based on client billing address and has been estimated based on the amounts billed to clients during the periods (in thousands).



	Three Months Ended
	March 31, 2015		March 31, 2014
United States	$	28,279	$	22,434
International	1,995		1,840
Total revenue	$	30,274	$	24,274

The following table summarizes total property and equipment, net in the respective locations (in thousands).



	March 31, 2015		December 31, 2014
United States	$	10,415	$	10,625
International	2,011		1,946
Property and equipment, net	$	12,426	$	12,571

Fair Value Measurements - Schedule of Assets Carried at Fair Value (Details) - U.S. Treasury bills - USD ($) $ in Thousands	Mar. 31, 2015	Dec. 31, 2014
Short-term Investments [Abstract]
U.S. Treasury bills	$ 19,999	$ 20,000
Level 1
Short-term Investments [Abstract]
U.S. Treasury bills	$ 19,999	$ 20,000

Short-Term Investments (Details) $ in Thousands	3 Months Ended
Short-Term Investments (Details) $ in Thousands	Mar. 31, 2015 USD ($)
Schedule of Short-Term Investments [Line Items]
Short-term investments remaining maturity	44 days
U.S. Treasury bills
Schedule of Short-Term Investments [Line Items]
Amortized Cost	$ 20,000
Gross Unrealized Gains	0
Gross Unrealized Losses	(1)
Aggregate Fair Value	$ 19,999

Financial Statement Components - Schedule of Accounts Receivable (Details) - USD ($) $ in Thousands	Mar. 31, 2015	Dec. 31, 2014
Accounts Receivable [Line Items]
Allowance for doubtful accounts	$ (30)	$ (65)
Accounts receivable, net	8,719	8,335
Billed Revenues
Accounts Receivable [Line Items]
Trade accounts receivable	8,000	7,482
Unbilled Revenues, net of advance client deposits
Accounts Receivable [Line Items]
Trade accounts receivable	$ 749	$ 918

Financial Statement Components - Schedule of Property and Equipment (Details) - USD ($) $ in Thousands	Mar. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment
Property and equipment	$ 29,676	$ 28,197
Accumulated depreciation and amortization	(17,250)	(15,626)
Property and equipment, net	12,426	12,571
Computer and Network Equipment
Property, Plant and Equipment
Property and equipment	25,590	24,292
Computer Software
Property, Plant and Equipment
Property and equipment	2,439	2,264
Furniture and Fixtures
Property, Plant and Equipment
Property and equipment	1,036	1,030
Leasehold Improvements
Property, Plant and Equipment
Property and equipment	$ 611	$ 611

Financial Statement Components - Schedule of Capital Leased Property and Equipment (Details) - USD ($) $ in Thousands	Mar. 31, 2015	Dec. 31, 2014
Financial Statement Components [Abstract]
Gross	$ 22,328	$ 21,025
Less: accumulated depreciation and amortization	(11,983)	(10,609)
Total	$ 10,345	$ 10,416

Financial Statement Components - Schedule of Accrued and Other Current Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2015	Dec. 31, 2014
Financial Statement Components [Abstract]
Accrued expenses	$ 2,245	$ 2,240
Accrued compensation and benefits	5,862	5,078
Accrued and other current liabilities	$ 8,107	$ 7,318

Financial Statement Components - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Financial Statement Components [Abstract]
Depreciation and amortization expense	$ 1.6	$ 1.5
Letter of credit related to insurance policy
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash	$ 0.2		$ 0.1
Letter of credit related to lease obligation
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash			$ 0.7

Intangible Assets - Schedule of Intangible Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2015	Dec. 31, 2014
Acquired Finite-Lived Intangible Assets
Gross Carrying Amount	$ 3,170	$ 3,170
Accumulated Amortization	(745)	(617)
Total	2,425	2,553
Developed technology
Acquired Finite-Lived Intangible Assets
Gross Carrying Amount	2,460	2,460
Accumulated Amortization	(511)	(423)
Total	1,949	2,037
Customer relationships
Acquired Finite-Lived Intangible Assets
Gross Carrying Amount	520	520
Accumulated Amortization	(151)	(125)
Total	369	395
Domain names
Acquired Finite-Lived Intangible Assets
Gross Carrying Amount	50	50
Accumulated Amortization	(15)	(12)
Total	35	38
Non-compete agreements
Acquired Finite-Lived Intangible Assets
Gross Carrying Amount	140	140
Accumulated Amortization	(68)	(57)
Total	$ 72	$ 83

Intangible Assets - Schedule of Expected Future Amortization Expense of Intangible Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2015	Dec. 31, 2014
Goodwill and Intangible Assets Disclosure [Abstract]
Remainder of 2015	$ 384
2016	503
2017	465
2018	442
2019	351
2020	280
Total	$ 2,425	$ 2,553

Intangible Assets Intangible Assets - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Intangible Assets, Net (Excluding Goodwill) [Abstract]
Amortization of Intangible Assets	$ 0.1	$ 0.1

Long-Term Debt - Narrative (Details)	1 Months Ended
Long-Term Debt - Narrative (Details)	Dec. 31, 2014 USD ($)	Feb. 28, 2014 USD ($) lender $ / shares shares	Oct. 31, 2013 USD ($) $ / shares shares	Jul. 31, 2013 USD ($) installment	Mar. 31, 2015 USD ($) shares	Sep. 30, 2014 USD ($)	Apr. 03, 2014 $ / shares shares
Debt Instrument
Revolving line of credit	$ 12,500,000				$ 12,500,000
Long-term debt, gross	39,640,000				38,858,000
Discount on debt	1,216,000				1,132,000
Loan and Security Agreement \| Revolving Credit Facility
Debt Instrument
Credit facility, maximum borrowing capacity	$ 20,000,000.0				20,000,000.0	$ 12,500,000.0
Debt Instrument, Interest Rate, Increase (Decrease)	(0.75%)
Debt Instrument, Covenant Terms, Minimum Required Cash on Deposit at Lender	$ 7,500,000.0				7,500,000.0	$ 2,000,000.0
Revolving line of credit					12,500,000
Credit facility, remaining borrowing capacity					7,500,000
Loan and Security Agreement \| Revolving Credit Facility \| Prime Rate
Debt Instrument
Debt instrument, basis spread	0.50%
Loan and Security Agreement \| Term Loan
Debt Instrument
Credit facility, amount borrowed			$ 5,000,000.0
Discount on debt			$ 100,000
Loan and Security Agreement \| Term Loan \| Prime Rate
Debt Instrument
Debt instrument, basis spread			1.50%
2014 Loan and Security Agreement \| Term Loan
Debt Instrument
Credit facility, maximum borrowing capacity		$ 30,000,000.0
Number of lenders \| lender		2
Credit facility, remaining borrowing capacity					10,000,000.0
Credit facility, minimum incremental borrowing amount					$ 1,000,000.0
Debt, payment terms		Monthly principal payments are due beginning in February 2016 based on 1/60th of the outstanding balance at that time and will continue until all remaining principal outstanding under the term loan becomes due and payable in February 2019.
2014 Loan and Security Agreement \| Term Loan \| Prime Rate
Debt Instrument
Term loan, minimum interest rate		10.00%
2014 Loan and Security Agreement \| Term Loan \| London Interbank Offered Rate (LIBOR)
Debt Instrument
Debt instrument, basis spread		9.00%
Tranche One \| Term Loan
Debt Instrument
Credit facility, maximum borrowing capacity		$ 20,000,000.0
Discount on debt		1,000,000
Payments of debt issuance costs		$ 400,000
Promissory Note
Debt Instrument
Promissory note, carrying value	$ 2,600,000
Series D-2 Convertible Preferred Stock \| Loan and Security Agreement \| Term Loan
Debt Instrument
Warrants issued \| shares			52,054
Warrants outstanding, exercise price (in USD per share) \| $ / shares			$ 1.441
Common Stock
Debt Instrument
Warrants outstanding upon IPO \| shares					359,596
Common Stock \| Loan and Security Agreement \| Term Loan
Debt Instrument
Warrants outstanding, exercise price (in USD per share) \| $ / shares							$ 5.76
Warrants outstanding upon IPO \| shares							13,013
Common Stock \| 2014 Loan and Security Agreement \| Term Loan
Debt Instrument
Warrants issued \| shares		177,865
Warrants outstanding, exercise price (in USD per share) \| $ / shares		$ 10.12
Common Stock \| Tranche One \| Term Loan
Debt Instrument
Warrants vested, shares \| shares		118,577
Notes Payable \| Loan and Security Agreement
Debt Instrument
Long-term debt, gross	4,500,000				$ 4,000,000
Notes Payable \| 2014 Loan and Security Agreement
Debt Instrument
Long-term debt, gross	$ 20,000,000				20,000,000
Notes Payable \| Promissory Note
Debt Instrument
Promissory note issued				$ 4,100,000
Promissory note, stated interest rate				12.75%
Promissory note, number of monthly payments \| installment				42
USF obligations \| Promissory Note
Debt Instrument
Promissory note issued				$ 4,100,000
Promissory note, carrying value					$ 2,400,000
Common Stock Warrant \| 2014 Loan and Security Agreement \| Term Loan
Debt Instrument
Class of warrant or right, vesting period (in years)		10 years
Class of Warrant or Right, Number of Securities Called by Warrants or Rights, Unvested \| shares					59,288

Long-Term Debt - Schedule of Outstanding Debt (Details) - USD ($) $ in Thousands	Mar. 31, 2015	Dec. 31, 2014
Schedule of ST and LT Debt [Line Items]
Long-term Debt, Gross	$ 38,858	$ 39,640
Less: discount	(1,132)	(1,216)
Long-term Debt	37,726	38,424
Less: current portion of debt	3,528	3,146
Total debt, less current portion	34,198	35,278
Line of Credit
Schedule of ST and LT Debt [Line Items]
Long-term Debt, Gross	12,500	12,500
2014 Loan and Security Agreement \| Notes Payable
Schedule of ST and LT Debt [Line Items]
Long-term Debt, Gross	20,000	20,000
2013 Loan and Security Agreement \| Notes Payable
Schedule of ST and LT Debt [Line Items]
Long-term Debt, Gross	4,000	4,500
Promissory note to USAC \| Notes Payable
Schedule of ST and LT Debt [Line Items]
Long-term Debt, Gross	$ 2,358	$ 2,640

Long-Term Debt - Schedule of Maturities of Debt (Details) - USD ($) $ in Thousands	Mar. 31, 2015	Dec. 31, 2014
Debt Disclosure [Abstract]
Remainder of 2015	$ 2,398
2016	19,507
2017	4,620
2018	4,000
2019	8,333
Total	$ 38,858	$ 39,640

Stockholders' Equity - Capital Structure Narrative (Details) - $ / shares	Mar. 31, 2015	Dec. 31, 2014
Equity [Abstract]
Common Stock, shares authorized	450,000,000	450,000,000
Common Stock, par value	$ 0.001	$ 0.001
Common Stock, shares issued	49,611,533	49,322,000
Common Stock, shares outstanding	49,611,533	49,322,000
Preferred Stock, shares authorized	5,000,000	5,000,000
Preferred Stock, par value	$ 0.001	$ 0.001
Preferred Stock, shares issued	0	0
Preferred Stock, shares outstanding	0	0

Stockholders' Equity - Common Stock Subject to Forfeiture Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended		3 Months Ended
	Oct. 31, 2014	Oct. 31, 2013	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Schedule of Restricted Stock [Line Items]
Stock-based compensation expense			$ 2,235	$ 1,196
Restricted Stock [Member] \| SoCoCare
Schedule of Restricted Stock [Line Items]
Restricted common stock issued in period, shares		118,577
Percentage of shares vested	50.00%
Grant date fair value, per share		$ 8.48
Stock-based compensation expense			$ 200	$ 200
Restricted common stock outstanding, shares			21,384		59,289
Vesting period 1 \| Restricted Stock [Member] \| SoCoCare
Schedule of Restricted Stock [Line Items]
Number of shares vested			37,905
Vesting period 2 \| Restricted Stock [Member] \| SoCoCare
Schedule of Restricted Stock [Line Items]
Number of shares vested			21,384

Stockholders' Equity - Warrants (Details) - Common Stock	3 Months Ended
	Mar. 31, 2015 $ / shares shares
Class of Warrant or Right
Warrants outstanding \| shares	359,596
Outstanding warrants exercise price, weighted-average \| $ / shares	$ 5.59
Minimum
Class of Warrant or Right
Warrant expiration date	February 2020
Maximum
Class of Warrant or Right
Warrant expiration date	February 2024

Stockholders' Equity - Common Stock Reserved for Future Issuance (Details) - shares	Mar. 31, 2015	Apr. 03, 2014
Class of Stock
Shares of common stock reserved for future issuance	15,682,000
Stock options
Class of Stock
Shares of common stock reserved for future issuance	6,891,000
Restricted Stock Units
Class of Stock
Shares of common stock reserved for future issuance	1,458,000
Warrant
Class of Stock
Shares of common stock reserved for future issuance	360,000
2014 Equity Incentive Plan
Class of Stock
Shares of common stock reserved for future issuance	5,756,000
Employee Stock Purchase Plan
Class of Stock
Shares of common stock reserved for future issuance	1,217,093	880,000

Stockholders' Equity - Equity Incentive Plans (Details) - 2014 Equity Incentive Plan - shares	Mar. 31, 2015	Jan. 01, 2015	Mar. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award
Automatic annual increase in common stock reserved for issuance, percentage		5.00%
Automatic annual increase in common stock reserved for issuance, shares		2,466,124
Common Stock
Share-based Compensation Arrangement by Share-based Payment Award
Number of shares authorized for issuance	5,756,262		5,300,000

Stockholders' Equity - Stock Option Activities (Details) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2015 USD ($) $ / shares shares
Options Outstanding, Weighted Average Exercise Price [Roll Forward]
Fair market value of common stock	$ 5.56
Stock options
Options Outstanding [Roll Forward]
Outstanding, beginning balance \| shares	7,164
Options granted \| shares	0
Options exercised \| shares	(209)
Options forfeited or expired \| shares	(64)
Outstanding, ending balance \| shares	6,891
Options Outstanding, Weighted Average Exercise Price [Roll Forward]
Outstanding, beginning balance, weighted average exercise price (in USD per share)	$ 4.34
Options granted, weighted average exercise price (in USD per share)	0.00
Options exercised, weighted average exercise price (in USD per share)	0.55
Options forfeited or expired, weighted average exercise price (in USD per share)	6.35
Outstanding, ending balance, weighted average exercise price (in USD per share)	$ 4.44
Outstanding, ending balance, weighted average remaining contractual life	7 years 2 months 9 days
Outstanding, ending balance, aggregate intrinsic value \| $	$ 15,714

Stockholders' Equity - RSU Activities (Details) - Restricted stock units shares in Thousands	3 Months Ended
	Mar. 31, 2015 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award
Beginning Balance, Number of shares outstanding \| shares	1,370
RSUs granted, in shares \| shares	188
RSUs vested and released,in shares \| shares	(79)
RSUs forfeited, in shares \| shares	(21)
Ending Balance, Number of shares outstanding \| shares	1,458
Beginning Balance, Weighted Average Grant Date Fair Value Per Share \| $ / shares	$ 5.21
Weighted Average Grant Date Fair Value Per Share, RSUs granted \| $ / shares	4.56
Weighted Average Grant Date Fair Value Per Share, RSUs vested and released \| $ / shares	5.31
Weighted Average Grant Date Fair Value Per Share, RSUs forfeited \| $ / shares	4.99
Ending Balance, Weighted Average Grant Date Fair Value Per Share \| $ / shares	$ 5.13

Stockholders' Equity - ESPP (Details) - shares	Mar. 31, 2015	Jan. 01, 2015	Apr. 03, 2014
Share-based Compensation Arrangement by Share-based Payment Award
Shares of common stock reserved for future issuance	15,682,000
ESPP
Share-based Compensation Arrangement by Share-based Payment Award
Shares of common stock reserved for future issuance	1,217,093		880,000
Automatic annual increase in common stock reserved for issuance, percentage		1.00%
Maximum annual increase of shares reserved		1,000,000
Automatic annual increase in common stock reserved for issuance, shares		493,224

Stockholders' Equity - Stock-based Compensation (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Stock-based Compensation Expense
Stock-based compensation expense	$ 2,235	$ 1,196
Cost of Revenue
Stock-based Compensation Expense
Stock-based compensation expense	188	87
Research and Development
Stock-based Compensation Expense
Stock-based compensation expense	574	350
Selling and Marketing
Stock-based Compensation Expense
Stock-based compensation expense	524	326
General and Administrative
Stock-based Compensation Expense
Stock-based compensation expense	949	$ 433
Stock options
Stock-based Compensation Expense
Unrecognized stock-based compensation expense	$ 9,710
Weighted-average amortization period	2 years 8 months 9 days
Restricted Stock Units
Stock-based Compensation Expense
Unrecognized stock-based compensation expense	$ 5,280
Weighted-average amortization period	3 years 4 months 28 days
Employee Stock Purchase Plan
Stock-based Compensation Expense
Unrecognized stock-based compensation expense	$ 131
Weighted-average amortization period	1 month 15 days

Stockholders' Equity - Option & ESPP Valuation Assumptions (Details) - Stock options	3 Months Ended
	Mar. 31, 2014
Class of Stock
Expected term (years)	6 years 29 days
Volatility	56.00%
Risk-free interest rate	1.80%
Dividend yield	0.00%

Net Loss Per Share - Basic and Diluted Net Loss Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Earnings Per Share [Abstract]
Net loss	$ (8,903)	$ (8,320)
Weighted-average shares used in computing basic and diluted net loss per share (in shares)	49,433	5,608
Basic and diluted net loss per share (in USD per share)	$ (0.18)	$ (1.48)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

Net Loss Per Share - Antidilutive Securities Excluded from Computation of Diluted Net Loss Per Share (Details) - shares shares in Thousands	Mar. 31, 2015	Mar. 31, 2014
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive securities excluded from EPS calculation	8,901	38,606
Convertible Preferred Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive securities excluded from EPS calculation		30,595
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive securities excluded from EPS calculation	6,891	7,345
Restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive securities excluded from EPS calculation	1,458
ESPP
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive securities excluded from EPS calculation	171
Warrants \| Common Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive securities excluded from EPS calculation	360
Warrants \| Convertible Preferred Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive securities excluded from EPS calculation		525
Common stock subject to repurchase or forfeiture
Antidilutive Securities Excluded from Computation of Earnings Per Share
Antidilutive securities excluded from EPS calculation	21	141

Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended
Income Taxes (Details) - USD ($) $ in Thousands	Mar. 31, 2015	Mar. 31, 2014
Income Tax Disclosure [Abstract]
Provision for income taxes	$ 18	$ 27

Commitments and Contingencies - Commitments (Details) - Capital Lease Obligations [Member] $ in Millions	3 Months Ended
	Mar. 31, 2015 USD ($)
Other Commitments [Line Items]
Capital lease future payment obligations incurred	$ 1.7
Capital lease future minimum payments, remainder of 2015	$ 0.4
Number of years remainder of minimum payments is due	2 years 3 months

Commitments and Contingencies - Contingencies (Details) - USD ($)	3 Months Ended
	Mar. 31, 2015	Sep. 30, 2014	Mar. 31, 2014	Dec. 31, 2014	Jul. 31, 2013
Universal Services Fund Liability [Abstract]
Accrued federal fees	$ 7,531,000			$ 7,215,000
Accrued charge by the Federal Communications Commission		$ 2,000,000
State and Local Taxes and Surcharges [Abstract]
General and Administrative Expense	7,275,000		$ 6,171,000
Accrued sales tax liability, current	1,221,000			297,000
Accrued sales tax liability, noncurrent	2,303,000			2,582,000
USF obligations
Universal Services Fund Liability [Abstract]
Maximum USF reimbursement payments	3,100,000
Accrued federal fees	5,500,000			5,200,000
USF obligations \| Periods Prior To 2008
Universal Services Fund Liability [Abstract]
Accrued federal fees	800,000			800,000
Potential Obligation for State Taxes on Usage Based Fees
State and Local Taxes and Surcharges [Abstract]
Payments for state and local taxes on usage-based fees	0		100,000
General and Administrative Expense	100,000		500,000
Accrued sales tax liability	3,300,000
Accrued sales tax liability, current	1,000,000
Accrued sales tax liability, noncurrent	2,300,000			2,600,000
Promissory Note
Universal Services Fund Liability [Abstract]
Promissory note, carrying value				$ 2,600,000
Promissory Note \| USF obligations
Universal Services Fund Liability [Abstract]
Promissory note issued					$ 4,100,000
Promissory note, carrying value	2,400,000
Out of Period Adjustment [Member] \| Potential Obligation for Sales Taxes on Sales of Subscription Services
State and Local Taxes and Surcharges [Abstract]
General and Administrative Expense	600,000
General and Administrative
Universal Services Fund Liability [Abstract]
Interest and penalty expense related to unpaid USF obligations			$ 100,000
Tentative FCC Penalty \| USF obligations
Universal Services Fund Liability [Abstract]
Accrued federal fees		$ 2,000,000
Soneet Kapila v. Five9, Inc.
Legal Matters
Damages sought	2,500,000
Soneet Kapila v. Five9, Inc. \| General and Administrative
Legal Matters
Litigation settlement	$ 99,000

Geographical Information - Schedule of Revenue and Property and Equipment by Geographic Region (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Revenues from External Customers and Long-Lived Assets
Revenue	$ 30,274	$ 24,274
Property and equipment, net	12,426		$ 12,571
United States
Revenues from External Customers and Long-Lived Assets
Revenue	28,279	22,434
Property and equipment, net	10,415		10,625
International
Revenues from External Customers and Long-Lived Assets
Revenue	1,995	$ 1,840
Property and equipment, net	$ 2,011		$ 1,946