Castlight Health (CSLT) 10-K 10 Mar 16 2015 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2015	Mar. 04, 2016	Jun. 30, 2015
Class of Stock [Line Items]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2015
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	FY
Trading Symbol	CSLT
Entity Registrant Name	CASTLIGHT HEALTH, INC.
Entity Central Index Key	1,433,714
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Accelerated Filer
Entity Public Float			$ 493,300,000
Class A [Member]
Class of Stock [Line Items]
Entity Common Stock, Shares Outstanding		54,517,785
Class B [Member]
Class of Stock [Line Items]
Entity Common Stock, Shares Outstanding		42,142,863

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 19,150	$ 17,425
Marketable securities	101,274	175,057
Accounts receivable, net	12,751	11,097
Deferred commissions	5,438	3,675
Prepaid expenses and other current assets	3,772	3,476
Total current assets	142,385	210,730
Property and equipment, net	6,896	3,630
Marketable securities, noncurrent	13,335	6,220
Restricted cash, noncurrent	1,000	0
Deferred commissions, noncurrent	4,923	2,563
Other assets	4,735	131
Total assets	173,274	223,274
Current liabilities:
Accounts payable	3,384	3,217
Accrued expenses and other current liabilities	4,550	5,791
Accrued compensation	11,477	10,455
Deferred revenue	26,590	20,708
Total current liabilities	46,001	40,171
Deferred revenue, noncurrent	7,522	6,652
Other liabilities, noncurrent	1,397	261
Total liabilities	$ 54,920	$ 47,084
Commitments and contingencies
Stockholders’ equity (deficit):
Preferred stock, $0.0001 par value; 10,000,000 and no shares authorized as of December 31, 2014 and 2013; no shares issued and outstanding as of December 31, 2014 and 2013	$ 0	$ 0
Additional paid-in capital	415,519	393,397
Accumulated other comprehensive income	(79)	(40)
Accumulated deficit	(297,096)	(217,176)
Total stockholders’ equity (deficit)	118,354	176,190
Total liabilities, convertible preferred stock and stockholders’ equity (deficit)	173,274	223,274
Convertible Preferred Stock [Member]
Current liabilities:
Convertible preferred stock, $0.0001 par value; no and 64,475,662 shares authorized as of December 31, 2014 and 2013; no and 64,475,633 shares issued and outstanding as of December 31, 2014 and 2013	0	0
Class A [Member]
Stockholders’ equity (deficit):
Common stock value issued	6	6
Class B [Member]
Stockholders’ equity (deficit):
Common stock value issued	$ 4	$ 3

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2015	Dec. 31, 2014
Preferred Stock
Par Value	$ 0.0001	$ 0.0001
Shares Authorized	10,000,000	10,000,000
Shares Issued	0	0
Shares Outstanding	0	0
Convertible Preferred Stock [Member]
Convertible Preferred Stock
Par Value	$ 0.0001	$ 0.0001
Shares Authorized	0	0
Shares Issued	0	0
Shares Outstanding	0	0
Class A [Member]
Common Stock
Par Value	$ 0.0001	$ 0.0001
Shares Authorized	200,000,000	200,000,000
Shares Issued	54,517,785	58,862,574
Shares Outstanding	54,517,785	58,862,574
Shares Subject to Repurchase	0	0
Class B [Member]
Common Stock
Par Value	$ 0.0001	$ 0.0001
Shares Authorized	800,000,000	800,000,000
Shares Issued	41,100,307	32,328,809
Shares Outstanding	41,100,307	32,328,809

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenue:
Subscription		$ 70,350	$ 41,602	$ 11,655
Professional services		4,965	4,003	1,318
Total revenue		75,315	45,605	12,973
Cost of revenue:
Cost of subscription	[1]	12,417	10,472	6,246
Cost of professional services	[1]	21,351	17,300	11,058
Total cost of revenue		33,768	27,772	17,304
Gross profit (loss)		41,547	17,833	(4,331)
Operating expenses:
Sales and marketing	[1]	67,414	62,065	33,742
Research and development	[1]	30,077	22,917	15,219
General and administrative	[1]	24,274	19,009	9,047
Total operating expenses		121,765	103,991	58,008
Operating loss		(80,218)	(86,158)	(62,339)
Other income, net		298	218	157
Net loss		$ (79,920)	$ (85,940)	$ (62,182)
Net loss per share, basic and diluted		$ (0.85)	$ (1.16)	$ (6.28)
Weighted-average shares used to compute basic and diluted net loss per share		93,753	74,381	9,895
[1]	Includes stock-based compensation expense as follows: Cost of subscription $283, $180, $5. Cost of professional services $2,175, $1,220, $120 Sales and marketing $7,705 , $5,933, $919. Research and development $3,498, $2,556 , $603. General and administrative $4,169, $4,312 , $780.

Consolidated Statements of Ope5

Consolidated Statements of Operations Parenthetical - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cost of subscription [Member]
Allocated Share-based Compensation Expense	$ 283	$ 180	$ 5
Cost of professional services [Member]
Allocated Share-based Compensation Expense	2,175	1,220	120
Sales and marketing [Member]
Allocated Share-based Compensation Expense	7,705	5,933	919
Research and development [Member]
Allocated Share-based Compensation Expense	3,498	2,556	603
General and administrative [Member]
Allocated Share-based Compensation Expense	$ 4,169	$ 4,312	$ 780

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Consolidated Statement of Comprehensive Loss:
Net loss	$ (79,920)	$ (85,940)	$ (62,182)
Other comprehensive loss:
Net change in unrealized loss on available-for-sale marketable securities	(39)	(40)	(34)
Reclassification adjustments for net realized gain (loss) on available-for-sale marketable securities	0	0	0
Other comprehensive loss	(39)	(40)	(34)
Comprehensive loss	$ (79,959)	$ (85,980)	$ (62,216)

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating activities:
Net loss	$ (79,920)	$ (85,940)	$ (62,182)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	2,024	1,354	633
Stock-based compensation	17,830	14,201	2,427
Amortization of deferred commissions	3,510	4,092	2,541
Accretion and amortization of marketable securities	1,385	1,489	714
Expense related to warrant	0	2,639	135
Changes in operating assets and liabilities:
Accounts receivable	(1,654)	(6,032)	(2,703)
Deferred commissions	(7,633)	(4,861)	(4,959)
Prepaid expenses and other current assets	807	(1,893)	(252)
Other assets	(479)	(2)	(109)
Accounts payable	646	147	868
Accrued expenses and other current liabilities	(1,475)	1,982	2,892
Deferred revenue	6,752	15,887	7,268
Accrued compensation	1,022	2,412	2,544
Other liabilities, noncurrent	317	(112)	119
Net cash used in operating activities	(56,868)	(54,637)	(50,064)
Increase (Decrease) in Restricted Cash	(1,000)	101
Investing activities:
Restricted cash			0
Payments to Acquire Interest in Subsidiaries and Affiliates	(4,125)	0	0
Purchase of property and equipment, net	(5,376)	(1,860)	(2,587)
Purchase of marketable securities	(119,867)	(230,316)	(42,288)
Sales of marketable securities	5,000	13,000	5,000
Maturities of marketable securities	180,111	76,527	72,135
Net cash provided by (used in) investing activities	54,743	(142,548)	32,260
Financing activities:
Proceeds from the exercise of stock options and warrants	3,944	3,294	864
Proceeds from initial public offering	0	189,943	0
Payments of deferred financing costs	(94)	(3,781)	(440)
Net cash provided by financing activities	3,850	189,456	424
Net increase (decrease) in cash and cash equivalents	1,725	(7,729)	(17,380)
Cash and cash equivalents at beginning of period	17,425	25,154	42,534
Cash and cash equivalents at end of period	19,150	17,425	25,154
Noncash investing and financing activity:
Vesting of early exercised stock options, restricted common stock, and warrants	0	(321)	(128)
Purchase of property and equipment, accrued but not paid	(165)	(600)	(122)
Deferred offering costs, accrued but not paid	$ 0	$ (94)	$ (927)

Consolidated Statements of Conv

Consolidated Statements of Convertible Preferred Stock and Stockholders' (Deficit)/Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Convertible Preferred Stock [Member]
Beginning balance (in shares) at Dec. 31, 2012						64,475,633
Beginning balance at Dec. 31, 2012						$ 180,423
Ending balance (in shares) at Dec. 31, 2013						64,475,633
Ending balance at Dec. 31, 2013						$ 180,423
Beginning balance (in shares) at Dec. 31, 2012		9,897,997,000
Beginning balance at Dec. 31, 2012	$ (65,388)	$ 1	$ 3,631	$ (69,054)	$ 34
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)		1,036,077,000
Exercise of stock options, net	564		564
Vesting of early exercised stock options, restricted common stock, and warrants	128		128
Early exercise of warrant issued (in shares)		60,000,000
Stock-based compensation	2,427		2,427
Expense related to warrant	135		135
Comprehensive loss	(62,216)			(62,182)	(34)
Ending balance (in shares) at Dec. 31, 2013		10,994,074,000
Ending balance at Dec. 31, 2013	(124,350)	$ 1	6,885	(131,236)	0
Increase (Decrease) in Temporary Equity [Roll Forward]
Conversion of preferred stock to common stock (in shares)		64,475,633,000				64,475,633
Conversion of preferred stock to common stock	180,423	$ 7	180,416			$ (180,423)
Ending balance (in shares) at Dec. 31, 2014						0
Ending balance at Dec. 31, 2014						$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Vesting of restricted common stock	21		21
Exercise of stock options (in shares)		2,956,676,000
Exercise of stock options, net	3,294		3,294
Vesting of early exercised stock options, restricted common stock, and warrants	321
Vesting of early exercised warrant issued	300		300
Stock-based compensation	14,215		14,215
Expense related to warrant	2,639		2,639
Issuance of common stock upon initial public offering, net of issuance costs (in shares)		12,765,000,000
Issuance of common stock upon initial public offering, net of issuance costs	185,628	$ 1	185,627
Comprehensive loss	(85,980)			(85,940)	(40)
Ending balance (in shares) at Dec. 31, 2014		91,191,383,000
Ending balance at Dec. 31, 2014	176,190	$ 9	393,397	(217,176)	(40)
Ending balance (in shares) at Dec. 31, 2015						0
Ending balance at Dec. 31, 2015						$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Vesting of restricted stock units (in shares)		295,468,000
Exercise of stock options (in shares)		4,131,241,000
Exercise of stock options, net	3,944	$ 1	3,943
Vesting of early exercised stock options, restricted common stock, and warrants	0
Stock-based compensation	18,179		18,179
Comprehensive loss	(79,959)			(79,920)	(39)
Ending balance (in shares) at Dec. 31, 2015		95,618,092,000
Ending balance at Dec. 31, 2015	$ 118,354	$ 10	$ 415,519	$ (297,096)	$ (79)

Organization and Description of

Organization and Description of Business	12 Months Ended
	Dec. 31, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Description of Business	Organization and Description of Business Description of Business Castlight offers a health benefits platform that engages employees to make better health care decisions and enables employers to communicate and measure their benefit programs. We provide a simple, personalized, and powerful way for employees to shop for and manage their health care. At the same time, we enable employers to understand their employees’ needs and guide them to the right care, right providers and right programs at the right time. Our comprehensive technology offering aggregates complex, large-scale data and applies sophisticated analytics to make health care data transparent and useful. We were incorporated in the State of Delaware in January 2008. Our principal executive offices are located in San Francisco, California. Initial Public Offering On March 19, 2014, we completed our initial public offering (IPO), in which we sold 12.8 million shares of Class B common stock at a price to the public of $16.00 per share. The aggregate offering price for shares sold in the offering was approximately $204.2 million . We raised approximately $185.6 million in net proceeds from the offering, after deducting underwriter discounts and commissions of approximately $14.3 million and other offering expenses of approximately $4.3 million .

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Basis of Presentation and Principles of Consolidation The consolidated financial statements were prepared in accordance with U.S. generally accepted accounting principles (GAAP). In the opinion of management, the information herein reflects all adjustments, consisting only of normal recurring adjustments, except as otherwise noted, considered necessary for a fair statement of results of operations, financial position and cash flows. The consolidated financial statements include the results of Castlight and its wholly owned U.S. subsidiary. Use of Estimates The preparation of consolidated financial statements in conformity with GAAP requires us to make certain estimates, judgments and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities as of the date of the financial statements, as well as the reported amounts of revenue and expenses during the reporting period. These estimates include, but are not limited to, the determination of the relative selling prices for our services, certain assumptions used in the valuation of our equity awards, and the capitalization and estimated useful life of internal-use software development costs. Actual results could differ from those estimates, and such differences could be material to our consolidated financial position and results of operations. Segment Information Our chief operating decision maker, our CEO, reviews the financial information presented on a consolidated basis for purposes of allocating resources and evaluating our financial performance. Accordingly, we have determined that we operate in a single reportable segment, cloud-based products. Revenue Recognition We derive our revenue from sales of cloud-based subscription service and professional services contracts. We sell subscriptions to our cloud-based subscription service through contracts that are generally three years in length. Our cloud-based subscription service contracts do not provide customers with the right to take possession of the software supporting the cloud-based service and, as a result, are accounted for as service contracts. We commence revenue recognition for our cloud-based subscription service and professional services when all of the following criteria are met: • there is persuasive evidence of an arrangement; • the service has been provided to the customer; • collection of the fees is reasonably assured; and • the amount of fees to be paid by the customer is fixed or determinable. Our subscription and professional service arrangements do not contain refund provisions for fees earned related to services performed. We do, however, have commitments under service-level agreements, as discussed under "Warranties and Indemnification" below. Subscription Revenue. Subscription revenue recognition commences on the date that our cloud-based service is made available to the customer, which is considered the launch date, provided all of the other criteria described above are met. Revenue is recognized based on the terms in our customer contracts, which can provide for (a) a variable periodic fee based upon the actual or contractual number of users that is recognized to revenue based on the actual or contractual number of users or (b) a fixed fee that is recognized to revenue on a straight-line basis over the contractual term of the arrangement. Some of our cloud-based subscription arrangements include performance incentives that are generally based upon employee engagement. Fees for performance incentives are considered contingent revenue, and are recognized over the remaining term of the related subscription arrangement commencing at the time they are earned. Professional Services Revenue. Professional services revenue is comprised of implementation services and communication services related to our cloud-based subscription service, as well as follow-on professional services to assist our customers in further adopting our cloud-based subscription service. Nearly all of our professional services are sold on a fixed-fee basis. We do not have standalone value for our implementation services. Accordingly, we recognize implementation services revenue in the same manner as the associated cloud-based subscription service, beginning on the launch date, provided all other criteria described above have been met. For follow-on professional services that are sold separately from the cloud-based subscription service, we recognize revenue as the services are delivered. Communication services have standalone value and the associated revenue is recognized over the contractual term, generally one year, commencing when the revenue recognition criteria have been met. Multiple Deliverable Arrangements. To date, we have generated substantially all our revenue from multiple deliverable arrangements consisting of multi-year cloud-based subscription services and professional services, including implementation services and communication services. For arrangements with multiple deliverables, we evaluate whether the individual deliverables qualify as separate units of accounting. In order to treat deliverables in a multiple deliverable arrangement as separate units of accounting, the deliverables must have standalone value upon delivery. If the deliverables have standalone value upon delivery, we account for each deliverable separately and revenue is recognized for the respective deliverables as they are delivered. If one or more of the deliverables do not have standalone value upon delivery, the deliverables that do not have standalone value are generally combined with our cloud-based subscription service, and revenue for the combined unit is recognized over the remaining term of the cloud-based subscription service. Our deliverables have standalone value if we or any other vendor sells a similar service separately. We have concluded that we have standalone value for our cloud-based subscription service as we sell these services separately through renewals and for our communication services as other vendors sell similar services separately. Conversely, we have concluded that our implementation services do not have standalone value, as we and others do not yet sell these services separately. Accordingly, we consider the separate units of accounting in our multiple deliverable arrangements to be the communication services and a combined deliverable comprised of cloud-based subscription services and implementation services. When multiple deliverables included in an arrangement are separable into different units of accounting, the arrangement consideration is allocated to the identified separate units of accounting based on their relative selling price. Multiple deliverable arrangements accounting guidance provides a hierarchy to use when determining the relative selling price for each unit of accounting. Vendor-specific objective evidence, or VSOE, of selling price, based on the price at which the item is regularly sold by the vendor on a standalone basis, should be used if it exists. If VSOE of selling price is not available, third-party evidence, or TPE, of selling price is used to establish the selling price if it exists. If TPE does not exist, we estimate the best estimated selling price, or BESP. VSOE does not currently exist for any of our deliverables. Additionally, we do not believe TPE is a practical alternative due to differences in our cloud-based subscription service compared to other parties and the availability of relevant third-party pricing information for our cloud-based subscription service and our other services. Accordingly, for arrangements with multiple deliverables that can be separated into different units of accounting, we allocate the arrangement fee to the separate units of accounting based on our BESP. The amount of arrangement fee allocated is limited by contingent revenue, if any. We determine BESP for our deliverables by considering our overall pricing objectives and market conditions. This includes evaluating our pricing practices, our target prices, the size of our transactions, historical sales and our go-to-market strategy. The determination of BESP is made through consultation with and approval by management. For financial statement presentation purposes, we allocate the fees from our combined units of accounting to subscription and professional services based upon their relative selling price. Costs of Revenue Cost of revenue consists of the cost of subscription revenue and cost of professional services revenue. Cost of subscription revenue primarily consists of data fees, employee-related expenses (including salaries, benefits and stock-based compensation) related to hosting costs of our cloud-based service, cost of subcontractors, expenses for service delivery (which includes call center support), allocated overhead, the costs of data center capacity, amortization of internal-use software and depreciation of owned computer equipment and software. Amortization of internal-use software was $0.2 million for the year ended December 31, 2015 . Cost of professional services revenue consists primarily of employee-related expenses associated with these services, the cost of subcontractors and travel costs. The time and costs of our customer implementations vary based on the source and condition of the data we receive from third parties, the configurations that we agree to provide and the size of the customer. Cash and Cash Equivalents Cash and cash equivalents consist of highly liquid investments with original maturities of three months or less from the date of purchase. Our cash and cash equivalents generally consist of investments in money market funds and U.S. agency obligations. Cash and cash equivalents are stated at fair value. Marketable Securities Our marketable securities consist of U.S. agency obligations and U.S. treasury securities, with maturities at the time of purchase of greater than three months. Marketable securities with remaining maturities in excess of one year are classified as noncurrent. We classify our marketable securities as available-for-sale at the time of purchase based on our intent and are recorded at their estimated fair value. Unrealized gains and losses for available-for-sale securities are recorded in other comprehensive loss. We evaluate our investments to assess whether those with unrealized loss positions are other than temporarily impaired. We consider impairments to be other than temporary if they are related to deterioration in credit risk or if it is likely we will sell the securities before the recovery of their cost basis. Realized gains and losses and declines in value judged to be other than temporary are determined based on the specific identification method and are reported in other income, net in the consolidated statements of operations. Accounts Receivable and Allowance for Doubtful Accounts Accounts receivable are recorded at the invoiced amount, net of allowances for doubtful accounts. The allowance for doubtful accounts is based on our assessment of the collectability of accounts. We regularly review the adequacy of the allowance for doubtful accounts by considering the age of each outstanding invoice and the collection history of each customer to determine whether a specific allowance is appropriate. Accounts receivable deemed uncollectable are charged against the allowance for doubtful accounts when identified. For all periods presented, the allowance for doubtful accounts was not significant. Deferred Commissions Deferred commissions are the incremental costs that are directly associated with the noncancellable portion of cloud-based subscription service contracts with customers and consist of sales commissions paid to our direct sales force. The commissions are deferred and amortized over the noncancellable terms of the related contracts. The deferred commission amounts are recoverable through the future revenue streams under the noncancellable customer contracts. Amortization of deferred commissions is included in sales and marketing expense in the consolidated statements of operations. Property and Equipment Property and equipment are stated at cost less accumulated depreciation. Depreciation is recorded using the straight-line method over the estimated useful lives of the respective asset as follows: Software 3–5 years Computer equipment 3 years Furniture and equipment 5–7 years Leasehold improvements Shorter of the lease term or the estimated useful lives of the improvements Maintenance and repairs are charged to expense as incurred, and improvements are capitalized. When assets are retired or otherwise disposed of, the cost and accumulated depreciation are removed from the accounts, and any resulting gain or loss is reflected in the consolidated statement of operations for the period realized. Restricted Cash Restricted cash consists of a letter of credit related to our leased office space. Internal-use Software For our development costs related to our cloud-based service, we capitalize costs incurred during the application development stage. Costs related to preliminary project and post-implementation stages are expensed as incurred. Capitalized software development costs are included as part of property, plant and equipment and are amortized on a straight-line basis over the technology's estimated useful life, which is generally three years. The amortization expense is recorded as a component of cost of subscription revenue. We capitalized software development costs totaling $2.6 million and $0.3 million for the years ended December 31, 2015 and 2014 , respectively. Deferred Revenue Deferred revenue consists of professional services and cloud-based subscription services that have been billed in advance of revenue being recognized. Additionally, deferred revenue consists of professional services that have been billed and delivered but the revenue is being deferred and recognized together with a cloud-based subscription contract as a single unit of accounting. We invoice our customers for our cloud-based subscription services based on the terms of the contract, which can be annual, quarterly or monthly installments. We invoice our customers for our professional services and the first year of communication services generally at contract execution. Deferred revenue that is anticipated to be recognized during the succeeding 12-month period is recorded as current deferred revenue, and the remaining portion is recorded as noncurrent. Stock-based Compensation All stock-based compensation to employees is measured based on the grant-date fair value of the awards and recognized in our consolidated statements of operations over the period during which the employee is required to perform services in exchange for the award (generally the vesting period of the award). We estimate the fair value of stock options granted using the Black-Scholes option valuation model. For restricted stock units, fair value is based on the closing price of our Class B common stock on the grant date. Compensation expense is recognized over the vesting period of the applicable award using the straight-line method. Compensation expense for non-employee stock options and warrants is calculated using the Black-Scholes option-pricing model and is recorded as the options vest. Options subject to vesting are required to be periodically revalued over their service period, which is generally the same as the vesting period. Income Taxes We account for income taxes using the liability method, under which deferred tax assets and liabilities are determined based on the future tax consequences attributable to differences between the financial reporting carrying amounts of existing assets and liabilities and their respective tax bases and tax credit and net operating loss carryforwards. Deferred tax assets and liabilities are measured using the enacted tax rates that are expected to be in effect when the differences are expected to reverse. We assess the likelihood that deferred tax assets will be recovered from future taxable income, and a valuation allowance is established when necessary to reduce deferred tax assets to the amounts more likely than not expected to be realized. We recognize and measure uncertain tax positions using a two-step approach. The first step is to evaluate the tax position taken or expected to be taken by determining if the weight of available evidence indicates that it is more likely than not that the tax position will be sustained in an audit, including resolution of any related appeals or litigation processes. The second step is to measure the tax benefit as the largest amount that is more than 50% likely to be realized upon ultimate settlement. Significant judgment is required to evaluate uncertain tax positions. We evaluate our uncertain tax positions on a regular basis. Our evaluations are based on a number of factors, including changes in facts and circumstances, changes in tax law, correspondence with tax authorities during the course of audit and effective settlement of audit issues. Warranties and Indemnification Our cloud-based service is generally warranted to be performed in a professional manner and in a manner that will comply with the terms of the customer agreements. Our arrangements generally include certain provisions for indemnifying customers against liabilities if there is a breach of a customer’s data or if our service infringes a third party’s intellectual property rights. To date, we have not incurred any material costs as a result of such indemnifications and have not accrued any liabilities related to such obligations in the financial statements. We have entered into service-level agreements with certain customers warranting defined levels of performance and response and permitting those customers to receive credits for prepaid amounts related to subscription services in the event that we fail to meet those levels. To date, we have not experienced any significant failures to meet defined levels of performance and response as a result of those agreements. We have also agreed to indemnify our directors and executive officers for costs associated with any fees, expenses, judgments, fines and settlement amounts incurred by any of these persons in any action or proceeding to which any of those persons is, or is threatened to be, made a party by reason of the person’s service as a director or officer, including any action by us, arising out of that person’s services as our director or officer or that person’s services provided to any other company or enterprise at our request. We maintain director and officer insurance coverage that would generally enable us to recover a portion of any future amounts paid. We may also be subject to indemnification obligation by law with respect to the actions of our employees under certain circumstances and in certain jurisdictions. Advertising Expenses Advertising is expensed as incurred. Advertising expense was $0.4 million , $0.7 million and $0.4 million for the years ended December 31, 2015 , 2014 and 2013 , respectively. Concentrations of Risk and Significant Customers Our financial instruments that are exposed to concentrations of credit risk consist primarily of cash and cash equivalents, marketable securities and accounts receivable. Although we deposit our cash with multiple financial institutions, our deposits, at times, may exceed federally insured limits. We serve our customers and users from outsourced data center facilities located in Colorado and Arizona. We have internal procedures to restore all of our production customer facing services in the event of disasters at the Colorado facility. Procedures utilizing currently deployed hardware, software and services at our disaster recovery location in Arizona allow our cloud-based service to be restored within 48 hours during the implementation of the procedures to restore services. Revenue from customers representing 10% or more of total revenue for the respective years, is summarized as follows: Year Ended December 31, 2015 2014 2013 Revenue: Customer A * 14 % 16 % * Less than 10% During the years ended December 31, 2015 , 2014 and 2013 , all of our revenue was generated by customers located in the United States. Accounts receivable from customers representing 10% or more of total accounts receivable as of the respective dates is summarized as follows: As of December 31, 2015 2014 Accounts Receivable: Customer B * 12 % Customer C 19 % 19 % * Less than 10% Recently Issued and Adopted Accounting Pronouncements In November 2015, the Financial Accounting Standards Board (FASB) issued a new accounting standard that would require companies and other organizations to include lease obligations on their balance sheets. The guidance will be effective for us beginning January 1, 2019. We are evaluating the accounting, transition and disclosure requirements of the standard and cannot currently estimate the financial statement impact of adoption. At this point in time, we do not intend to adopt the standard early. In April 2015, FASB issued new accounting guidance on Customer's Accounting for Fees Paid in a Cloud Computing Arrangement. This guidance is intended to help entities evaluate the accounting for fees paid by a customer in a cloud computing arrangement, primarily to determine whether the arrangement includes a sale or license of software. The guidance will be effective for us beginning January 1, 2016. Early adoption is permitted. We have elected not to early adopt. The adoption of this guidance is not expected to have a material impact on our consolidated financial statements. In May 2014, FASB issued ASU 2014-09 regarding ASC Topic 606, Revenue from Contracts with Customers. The standard provides principles for recognizing revenue for the transfer of promised goods or services to customers with the consideration to which the entity expects to be entitled in exchange for those goods or services. In August 2015, FASB deferred the effective date of the standard for all entities by one year. The standard will become effective for the annual reporting period (including interim reporting periods) beginning after December 15, 2017, and early adoption is permitted as of annual reporting periods (including interim periods) beginning after December 15, 2016. We are evaluating the accounting, transition and disclosure requirements of the standard and cannot currently estimate the financial statement impact of adoption. At this point in time, we do not intend to adopt the standard early.

Marketable Securities

Marketable Securities	12 Months Ended
	Dec. 31, 2015
Investments, Debt and Equity Securities [Abstract]
Marketable Securities	Marketable Securities At December 31, 2015 and December 31, 2014 , respectively, marketable securities consisted of the following (in thousands): Amortized Cost Unrealized Gains Unrealized Losses Fair Value December 31, 2015 U.S. agency obligations $ 83,763 $ — $ (48 ) $ 83,715 U.S. treasury securities 33,924 — (31 ) 33,893 Money market mutual funds 1,038 — — 1,038 118,725 — (79 ) 118,646 Included in cash and cash equivalents 4,038 — (1 ) 4,037 Included in marketable securities $ 101,334 $ — $ (60 ) $ 101,274 Included in marketable securities, noncurrent $ 13,353 $ — $ (18 ) $ 13,335 Amortized Cost Unrealized Gains Unrealized Losses Fair Value December 31, 2014 U.S. agency obligations $ 177,297 $ 4 $ (44 ) $ 177,257 U.S. treasury securities 5,580 1 — 5,581 Money market mutual funds 1,919 — — 1,919 184,796 5 (44 ) 184,757 Included in cash and cash equivalents 3,480 — — 3,480 Included in marketable securities $ 175,093 $ 5 $ (41 ) $ 175,057 Included in marketable securities, noncurrent $ 6,223 $ — $ (3 ) $ 6,220

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements We measure our financial assets and liabilities at fair value at each reporting period using a fair value hierarchy that requires that we maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. A financial instrument’s classification within the fair value hierarchy is based upon the lowest level of input that is significant to the fair value measurement. Three levels of inputs may be used to measure fair value: Level 1—Observable inputs that reflect quoted prices (unadjusted) for identical assets or liabilities in active markets. Level 2—Include other inputs that are directly or indirectly observable in the marketplace. Level 3—Unobservable inputs that are supported by little or no market activity. The fair value of marketable securities included in the Level 2 category is based on observable inputs, such as quoted prices for similar assets at the measurement date; quoted prices in markets that are not active; or other inputs that are observable, either directly or indirectly. These values were obtained from a third-party pricing service and were evaluated using pricing models that vary by asset class and may incorporate available trade, bid and other market information and price quotes from well-established third party pricing vendors and broker-dealers. There have been no changes in valuation techniques in the periods presented. We have no financial assets or liabilities measured using Level 3 inputs. There were no significant transfers between Levels 1 and 2 assets as of December 31, 2015 and December 31, 2014 . The following tables present information about our assets that are measured at fair value on a recurring basis using the above input categories (in thousands): Level 1 Level 2 Total December 31, 2015 Cash equivalents: Money market mutual funds $ 1,038 $ — $ 1,038 U.S. agency obligations — 3,000 3,000 Marketable securities: U.S. agency obligations — 80,715 80,715 U.S. treasury securities — 33,893 33,893 $ 1,038 $ 117,608 $ 118,646 Level 1 Level 2 Total December 31, 2014 Cash equivalents: Money market mutual funds $ 1,919 $ — $ 1,919 U.S. agency obligations — 1,561 1,561 Marketable securities: U.S. agency obligations — 175,696 175,696 U.S. treasury securities — 5,581 5,581 $ 1,919 $ 182,838 $ 184,757 Gross unrealized gains and losses for cash equivalents and marketable securities as of December 31, 2015 and December 31, 2014 were not material. We do not believe the unrealized losses represent other-than-temporary impairments based on our evaluation of available evidence as of December 31, 2015 . There were no realized gains or losses for the years ended December 31, 2015 and 2014 . As of December 31, 2015 and 2014 those securities with maturities at the time of purchase of greater than one year are reflected in the noncurrent portion of our consolidated balance sheets. Marketable securities on the balance sheets consist of securities with original or remaining maturities at the time of purchase of greater than three months, and the remainder of the securities is reflected in cash and cash equivalents. As of December 31, 2015 , all of our marketable securities mature within one to five years.

Prepaid Expenses and Other Curr

Prepaid Expenses and Other Current Assets	12 Months Ended
	Dec. 31, 2015
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Prepaid Expenses and Other Current Assets	Prepaid Expenses and Other Current Assets Prepaid expenses and other current assets consisted of the following (in thousands): As of December 31, 2015 2014 Prepaid expenses and advances $ 3,033 $ 2,285 Security deposit 228 211 Interest receivable on marketable securities 361 537 Other current assets 150 443 Total $ 3,772 $ 3,476

Property and equipment, net

Property and equipment, net	12 Months Ended
	Dec. 31, 2015
Property, Plant and Equipment [Abstract]
Property and equipment	Property and Equipment Property and equipment consisted of the following (in thousands): As of December 31, 2015 2014 Leasehold improvements $ 2,046 $ 1,058 Computer equipment 4,345 3,247 Software 885 874 Capitalization of internal-use software 2,925 291 Furniture and equipment 853 301 Total 11,054 5,771 Accumulated depreciation (4,158 ) (2,141 ) Property and equipment, net $ 6,896 $ 3,630 Depreciation and amortization expense for the years ended December 31, 2015 , 2014 and 2013 was $2.0 million , $1.4 million and $0.6 million , respectively. Depreciation is recorded on a straight-line basis.

Related Party Transactions (Not

Related Party Transactions (Notes)	12 Months Ended
	Dec. 31, 2015
Related Party Transaction [Line Items]
Related Party Transactions Disclosure [Text Block]	In the second quarter of 2015, we announced a strategic alliance with Lyra Health ("Lyra"), to develop and bring to market an integrated behavioral health solution. In connection with this strategic alliance, Castlight made an initial preferred stock investment in Lyra of $3.1 million . Additionally, we made a subsequent preferred stock investment in Lyra of $1.0 million in August 2015. Lyra is considered a related party to us because two of Lyra’s co-founders serve on our board of directors, and Castlight's chief executive officer serves on Lyra's board. An independent committee of Castlight's board of directors, comprised of directors without any involvement in any external behavioral health business initiatives, approved the strategic alliance with and investment in Lyra. Lyra Health was founded in 2015 to work with employers, health plans, and providers to improve behavioral health outcomes and plans to offer a complementary behavioral health service that combines technology with active care management to improve patient outcomes. As part of the strategic alliance Lyra's product will be integrated with Castlight Elevate for those customers who purchase both solutions. Castlight Elevate is an extension of our health benefits platform which enables employees to research behavioral health services, make educated treatment choices, and commence care. We have evaluated both the initial and additional investment transactions and have determined that Lyra is a variable interest entity (“VIE”) for Castlight. In determining that we are not the VIE's primary beneficiary, we considered qualitative and quantitative factors, including, but not limited to: which activities most significantly impact the VIE’s economic performance and which party controls such activities; the characteristics of our involvement; and the obligation or likelihood for us to provide incremental financial support. Based on our evaluation, we determined that Castlight and our related parties collectively have power and benefits of the operations of VIE; however, Castlight is not the party most closely associated to the VIE. Accordingly, we are not required to consolidate the operations of the VIE. Our maximum exposure to loss as a result of our involvement with this unconsolidated VIE is limited to our investment of $4.1 million and we are not obligated to provide incremental financial support to Lyra. The investment in Lyra is accounted for under the cost method and is included under other assets in our consolidated financial statements. We have not estimated the fair value of our investment because there have been no identified events or changes in circumstances that may have a significant adverse effect on the fair value of the investment. We assess our investment for impairment on a quarterly basis or based on facts or circumstances that may require us to reassess the fair value of our investment. Based on the facts and circumstances as of December 31, 2015 , we concluded that our investment was appropriately valued.

Accrued Compensation

Accrued Compensation	12 Months Ended
	Dec. 31, 2015
Compensation Related Costs [Abstract]
Accrued Compensation	Accrued Compensation Accrued compensation consisted of the following (in thousands): As of December 31, 2015 2014 Accrued bonuses $ 4,034 $ 4,728 Accrued commissions 5,212 3,035 Other benefits payable 2,231 2,692 Total $ 11,477 $ 10,455

Deferred Revenue

Deferred Revenue	12 Months Ended
	Dec. 31, 2015
Deferred Revenue Disclosure [Abstract]
Deferred Revenue	Deferred Revenue Deferred revenue consisted of the following (in thousands): As of December 31, 2015 2014 Subscription $ 18,029 $ 14,826 Professional services—implementation 5,254 2,974 Professional services—communications 3,307 2,908 Total current 26,590 20,708 Subscription 1,163 1,950 Professional services—implementation 5,367 4,327 Professional services—communications 992 375 Total noncurrent 7,522 6,652 Total $ 34,112 $ 27,360

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Leases and Contractual Obligations We lease office space under noncancellable operating leases in San Francisco, California and Sunnyvale, California. Contractual obligations relate to our service agreements for our data centers in Colorado and Arizona and other third party service providers. As of December 31, 2015 , the future minimum lease payments under noncancellable operating leases are as follows (in thousands): Operating Leases Contractual Obligations 2016 $ 3,369 $ 243 2017 3,073 — 2018 2,548 — 2019 2,624 — 2020 and later 3,830 — $ 15,444 $ 243 Our facility lease agreements generally provide for rental payments on a graduated basis and for options to renew, which could increase future minimum lease payments if exercised. We recognize rent expense on a straight-line basis over the lease period and have accrued for rent expense incurred but not paid. Rent expense for the years ended December 31, 2015 , 2014 and 2013 was $2.1 million , $1.2 million and $1.0 million , respectively. Legal Matters On April 2, April 16, April 29, and May 4, 2015, purported securities class action lawsuits were filed in the Superior Court of the State of California, County of San Mateo, against us, certain of our current and former directors, executive officers, significant stockholders and underwriters associated with our initial public offering (IPO). The lawsuits, which were consolidated on July 22, 2015, were brought by purported stockholders of our company seeking to represent a class consisting of all those who purchased our stock pursuant or traceable to the Registration Statement and Prospectus issued in connection with our IPO. A consolidated complaint (“Complaint”) was filed on July 23, 2015, which purports to allege claims under Sections 11, 12(a)(2) and 15 of the Securities Act of 1933. On September 22, 2015 we filed a Demurrer to the Complaint. After briefing and argument, the Court overruled the demurrer as to Plaintiffs’ claims under Sections 11 and 15 and granted with leave amend the demurrer to Plaintiff’s claims under Section 12(a)(2). The Complaint seeks unspecified damages and other relief. Discovery in the action is ongoing. We believe that the claims are without merit and intend to defend the action vigorously. From time to time, we may become subject to other legal proceedings, claims or litigation arising in the ordinary course of business. In addition, we may receive letters alleging infringement of patents or other intellectual property rights. We do not believe that any liability from any reasonably foreseeable disposition of these legal actions and claims, individually or in the aggregate, would have a material effect on our business, operating results, cash flows or financial condition. The lawsuits described above are still in their early stages and the final outcome, including our liability, if any, with respect to the claims in the lawsuits, is uncertain. If an unfavorable outcome were to occur in the litigation, the impact could be material to our business, financial condition, cash flow or results of operations, depending on the specific circumstances of the outcome. We cannot make a reasonable estimate of the potential loss or range of loss, if any, arising from these matters. We accrue for loss contingencies when it is both probable that we will incur the loss and when we can reasonably estimate the amount of the loss or range of loss. If we determine that a loss is reasonably possible and can reasonably estimate the range of the loss, then we will disclose the range of the possible loss.

Stockholders' Equity (Deficit)

Stockholders' Equity (Deficit)	12 Months Ended
	Dec. 31, 2015
Equity and Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stockholders' Equity (Deficit)	Stockholders’ Equity Initial Public Offering On March 19, 2014, we completed our IPO, in which we sold 12.8 million shares of Class B common stock at a price to the public of $16.00 per share. Upon the consummation of the IPO, all outstanding shares of convertible preferred stock were converted into shares of Class A common stock. Employee Equity Plans We adopted a 2014 Equity Incentive Plan (EIP) that became effective on March 12, 2014 and serves as the successor to our 2008 Stock Incentive Plan. Shares issued under the 2008 Stock Plan were Class A common stock and shares issued under the EIP are Class B common stock. Our 2014 Equity Incentive Plan authorizes the award of stock options, restricted stock awards (RSAs), stock appreciation rights (SARs), restricted stock units (RSUs), performance awards and stock bonuses. We began granting RSUs in the fourth quarter of 2014. We adopted a 2014 Employee Stock Purchase Plan (ESPP) that became effective on March 13, 2014 that enables eligible employees to purchase shares of our Class B common stock at a discount. We have not yet established a start date of the initial purchasing period under the ESPP. The following table summarizes activities for stock options: Options Outstanding Number of Shares Outstanding Weighted- Average Exercise Price Weighted- Average Remaining Contractual Life in Years Aggregate Intrinsic Value Balance at December 31, 2014 16,392,539 $ 4.40 7.3 $ 128,541 Stock options granted 491,900 $ 8.95 Stock options exercised (4,177,555 ) $ 1.02 Stock options canceled and forfeited (3,145,171 ) $ 5.87 Balance at December 31, 2015 9,561,713 $ 5.62 6.9 $ 16,694 Vested or expected to vest December 31, 2015 9,022,878 $ 5.50 6.8 $ 16,149 Exercisable as of December 31, 2015 5,416,829 $ 3.99 6.0 $ 12,497 The total grant-date fair value of stock options granted during the years ended December 31, 2015 , 2014 and 2013 was $2.5 million , $39.9 million and $17.0 million , respectively. T he total grant-date fair value of stock options vested during the years ended December 31, 2015 , 2014 and 2013 was $10.8 million , $9.7 million and $1.7 million , respectively. The total intrinsic value of the options exercised during the years ended December 31, 2015 , 2014 and 2013 , was $25.3 million , $31.1 million and $1.8 million , respectively. The intrinsic value is the difference of the current fair value of the stock and the exercise price of the stock option. As of December 31, 2015 , we had $19.0 million in unrecognized compensation cost related to non-vested stock options, which is expected to be recognized over a weighted-average period of approximately 2.4 years. The following table summarizes activities for RSUs: Restricted Stock Units Outstanding Number of shares Weighted Average Grant-Date Fair Value Balance at December 31, 2014 1,398,893 $ 11.06 Restricted stock units granted 6,507,250 $ 7.24 Restricted stock units vested (295,468 ) $ 10.70 Restricted stock units canceled and forfeited (925,557 ) $ 9.06 Balance at December 31, 2015 6,685,118 $ 7.63 The total grant-date fair value of RSUs granted during the years ended December 31, 2015 and 2014 was $47.1 million and $15.7 million, respectively. T he total grant-date fair value of RSUs vested during the year ended December 31, 2015 was $3.2 million. No RSUs vested during the year ended December 31, 2014 . As of December 31, 2015 , we had $43.6 million in unrecognized compensation cost related to non-vested RSUs, which is expected to be recognized over a weighted-average period of approximately 2.3 years. Stock-based compensation capitalized to internal-use software for December 31, 2015 was $0.3 million . Stock-Based Compensation to Employees All stock-based compensation to employees is measured based on the grant-date fair value of the awards and is generally recognized in our statement of operations over the period during which the employee is required to perform services in exchange for the award (generally the vesting period of the award). We estimate the fair value of stock options granted using the Black-Scholes option-valuation model. For restricted stock units, fair value is based on the closing price of our Class B common stock on the grant date. Compensation cost is generally recognized over the vesting period of the applicable award using the straight-line method. The assumptions used in the Black-Scholes option-valuation model were determined as follows: Volatility. Since we do not have a trading history for our Class B common stock, the expected volatility was derived from the historical stock volatilities of peer group companies within our industry. I n evaluating peer companies, we considered factors such as nature of business, customer base, service offerings and markets served. Risk-Free Interest Rate. The risk-free rate that we used is based on U.S. Treasury zero-coupon issues with remaining terms similar to the expected term on the options. Expected Life. The expected term represents the period that our stock-based awards are expected to be outstanding. The expected term assumptions were determined based on the vesting terms, exercise terms and contractual lives of the options. Dividend Yield. We have never declared or paid any cash dividends and do not plan to pay cash dividends in the foreseeable future, and therefore, we use an expected dividend yield of zero. Fair Value of Common Stock. Prior to our initial public offering in March 2014, our board of directors considered numerous objective and subjective factors to determine the fair value of our Class A common stock at each grant date. These factors included, but were not limited to, (i) contemporaneous valuations of Class A common stock performed by unrelated third-party specialists; (ii) the prices for our Preferred Stock sold to outside investors; (iii) the rights, preferences and privileges of our Preferred Stock relative to our Class A common stock; (iv) the lack of marketability of our Class A common stock; (v) developments in the business; and (vi) the likelihood of achieving a liquidity event, such as an initial public offering or a merger or acquisition of our Company, given prevailing market conditions. S ince our initial public offering, we have used the market closing price for our Class B common stock as reported on the New York Stock Exchange to determine the fair value of our common stock. In addition to assumptions used in the Black-Scholes option-pricing model, we must also estimate a forfeiture rate to calculate the stock-based compensation for our awards. Our forfeiture rate is based on an analysis of our actual forfeitures. We use historical data to estimate pre-vesting option forfeitures and record stock-based compensation expense only for those awards that are expected to vest. The fair value of each option grant was estimated on the date of grant using the Black-Scholes option-valuation model with the following assumptions and fair value per share: Year Ended December 31, 2015 2014 2013 Volatility 53% 60% 57.8%-60% Expected life (in years) 6.2 5.0-6.3 5.0-7.2 Risk-free interest rate 1.38%-1.91% 1.53%-2.05% 0.7%-1.8% Dividend yield —% —% —% Weighted-average fair value of underlying common stock $8.95 $14.74 $3.02 Warrants On December 11, 2013, we issued a warrant to purchase an aggregate of 175,000 shares of Class A common stock at an exercise price of $5.00 per share to a third-party service provider. The warrant provides for an early exercise right and has a 10 year term. As of December 31, 2014 , the warrants were fully vested. Expense for the warrants is calculated using the Black-Scholes option-pricing model and is recorded over the service performance period, which is the same as the vesting period. For the year ended December 31, 2014 , we recorded $2.6 million in expense associated with this warrant. The expense for the year ended December 31, 2013 was immaterial.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The components of loss from continuing operations before income taxes were generated solely in the United States as follows (in thousands): Year Ended December 31, 2015 2014 2013 United States $ (79,920 ) $ (85,940 ) $ (62,182 ) As a result of our history of net operating losses and full valuation allowance against our deferred tax assets, there was no current or deferred income tax provision for the years ended December 31, 2015 , 2014 and 2013 . Reconciliations of the statutory federal income tax rate and our effective tax rate consist of the following (in thousands): Year Ended December 31, 2015 2014 2013 Tax at federal statutory rate $ (27,173 ) $ (29,220 ) $ (21,142 ) State statutory rate (net of federal benefit) (1,560 ) (1,728 ) (1,921 ) Non-deductible stock compensation 2,334 (19 ) 619 Change in valuation allowance 24,332 30,571 22,184 Other 2,067 396 260 $ — $ — $ — Significant components of our deferred tax assets and liabilities were as follows (in thousands): As of December 31, Deferred tax assets: 2015 2014 Net operating loss carryforwards $ 93,165 $ 72,984 Deferred rent 235 127 Accrued bonus — 68 Accrued compensation 326 539 Stock-based compensation 6,224 3,266 Other reserves and accruals 4 2 Property and equipment 322 16 Deferred revenue 3,017 2,173 103,293 79,175 Valuation allowance (103,293 ) (79,175 ) Net deferred tax assets $ — $ — We have provided a full valuation allowance for our deferred tax assets at December 31, 2015 and 2014 , due to the uncertainty surrounding the future realization of such assets. Therefore, no benefit has been recognized for the net operating loss carryforwards and other deferred tax assets. The valuation allowance increased by $24.1 million and $30.6 million during the years ended December 31, 2015 and 2014 , respectively. For the years ended December 31, 2015 and 2014 , we recorded no tax benefits related to stock-based compensation. As of December 31, 2015 , we have approximately $250.0 million of federal and $155.2 million of state net operating loss carryforwards available to offset future taxable income. If not utilized, the federal and state net operating loss carryforwards begin to expire in 2028 and 2017 , respectively. The deferred tax asset related to our net operating losses does not include amounts relating to the tax benefit of stock option exercises, which, when realized, will be recorded as a credit to additional paid-in capital. As of December 31, 2015 , we also had approximately $4.5 million and $5.1 million of research and development tax credit carryforwards available to reduce future taxable income if any, for federal and California purposes, respectively. The federal credit carryforwards expire beginning in 2028 and the California research credits do not expire and may be carried forward indefinitely. Our ability to utilize the net operating loss and tax credit carryforwards in the future may be subject to substantial restrictions in the event of past or future ownership changes as defined in Section 382 of the Internal Revenue Code and similar state tax laws. In the event we should experience an ownership change, as defined, utilization of our net operating loss carryforwards and tax credits could be limited. We evaluate tax positions for recognition using a more-likely-than-not recognition threshold, and those tax positions eligible for recognition are measured as the largest amount of tax benefit that is greater than 50% likely of being realized upon the effective settlement with a taxing authority that has full knowledge of all relevant information. A reconciliation of the beginning and ending amount of the gross unrecognized tax benefit is as follows (in thousands): Year Ended December 31, 2015 2014 2013 Gross unrecognized tax benefits at the beginning of the year $ 7,214 $ 4,513 $ 2,445 Increases for tax positions of prior years 133 871 — Decreases for tax positions of prior years (346 ) (831 ) — Increases for tax positions related to the current year 2,539 2,661 2,068 Gross unrecognized tax benefits at the end of the year $ 9,540 $ 7,214 $ 4,513 At December 31, 2015 , all unrecognized tax benefits are subject to a full valuation allowance and, if recognized, will not affect our tax rate. There were no material changes to the unrecognized tax benefits in the year ended December 31, 2015 , and we do not anticipate that the total amounts of unrecognized tax benefits will significantly increase or decrease in the next 12 months. Our policy is to include interest and penalties related to unrecognized tax benefits within our provision for income taxes. Due to our net operating loss position, we have not recorded an accrual for interest or penalties related to uncertain tax positions for the years ended December 31, 2015 , 2014 or 2013 .

Net Loss per Share

Net Loss per Share	12 Months Ended
	Dec. 31, 2015
Earnings Per Share [Abstract]
Net Loss per Share	Net Loss per Share Basic net loss per share is computed by dividing the net loss by the weighted-average number of shares of common stock outstanding during the period, less the weighted-average unvested common stock subject to repurchase. Diluted net loss per share is computed by giving effect to all potential shares of common stock, including Preferred Stock and outstanding stock options and warrants, to the extent dilutive. Basic and diluted net loss per share was the same for each period presented as the inclusion of all potential shares of common stock outstanding would have been anti-dilutive. When shares of both Class A and Class B common stock are outstanding, net loss is allocated based on the contractual participation rights of the Class A and Class B common stock as if the earnings for the year have been distributed. As the liquidation and dividend rights are identical, the net loss is allocated on a proportionate basis. As of December 31, 2013 , only shares of Class A common stock were outstanding and therefore no net loss was allocated. The following table presents the calculation of basic and diluted net loss per share for our common stock (in thousands, except per share data): Year Ended December 31, 2015 2014 2013 Class A Class B Class A Class B Class A Net loss $ (48,116 ) $ (31,804 ) $ (67,655 ) $ (18,285 ) $ (62,182 ) Weighted-average shares used to compute basic and diluted net loss per share 56,444 37,309 58,555 15,826 9,895 Basic and diluted net loss per share $ (0.85 ) $ (0.85 ) $ (1.16 ) $ (1.16 ) $ (6.28 ) The following securities were excluded from the calculation of diluted net loss per share for common stock because their effect would have been anti-dilutive for the periods presented (in thousands): Year Ended December 31, 2015 2014 2013 Convertible preferred stock — — 64,476 Stock options and restricted common stock 16,247 17,791 16,687 Warrants 115 115 175 $ 16,362 $ 17,906 $ 81,338

401(k) Plan

401(k) Plan	12 Months Ended
	Dec. 31, 2015
Compensation and Retirement Disclosure [Abstract]
401(k) Plan	401(k) Plan We have a qualified defined contribution plan under Section 401(k) of the Internal Revenue Code covering eligible employees. Under the plan, participating employees may defer up to 100% of their pre-tax earnings, subject to the Internal Revenue Service annual contribution limits. Effective January 1, 2015, we began matching a portion of the employee contributions. Our contribution expense in 2015 totaled $0.9 million .

Selected Quarterly Financial Da

Selected Quarterly Financial Data (unaudited)	12 Months Ended
	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Selected Quarterly Financial Data (unaudited)	Selected Quarterly Financial Data (unaudited) The following tables set forth selected unaudited quarterly consolidated statements of operations data for each of the eight quarters in years 2015 and 2014 (in thousands, except per share data): Quarter Ended Mar 31, Jun 30, Sept 30, Dec 31, Mar 31, Jun 30, Sept 30, Dec 31, Total revenue 8,376 10,533 12,209 14,487 15,951 18,510 19,539 21,315 Gross profit 1,793 3,116 5,054 7,870 8,779 10,256 10,852 11,660 Net loss $ (24,281 ) $ (21,776 ) $ (20,199 ) $ (19,684 ) $ (19,643 ) $ (21,212 ) $ (20,007 ) $ (19,058 ) Net loss per share, basic and diluted $ (0.90 ) $ (0.24 ) $ (0.23 ) $ (0.22 ) $ (0.21 ) $ (0.23 ) $ (0.21 ) $ (0.20 )

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2015
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events On January 12, 2016 , Castlight commenced a tender offer to eligible employees to exchange all options to purchase shares of Class A common stock and options to purchase shares of Class B common stock that were outstanding and unexercised as of that date with an exercise price of $6.76 or more per share. The exchange ratio for this offer was one ( 1 ) exchanged option for every one (1) new option granted, with the new option award vesting over five years from February 24, 2016 , the replacement grant date, in 60 monthly installments, subject to the employees' continued employment with Castlight. This tender offer expired on February 24, 2016 and was subject to the terms and conditions set forth in the Amended and Restated Offer to Exchange Certain Outstanding Option Awards for New Option Awards, dated January 28, 2016 , which was filed with the Securities Exchange Commission on January 28, 2016 . There were 132 employees eligible to tender options covering an aggregate of 2,881,013 shares of our Class A and Class B common stock, of which 108 employees tendered options covering 2,685,396 shares of Class A and Class B common stock at a weighted average exercise price of $11.03 , in exchange for options to purchase 2,685,396 shares of Class B common stock at an exercise price of $2.99 per share, the closing sale price reported on the New York Stock Exchange on February 24, 2016 . As of February 24, 2016 the incremental expense related to this offer was 1.8 million , which will be recognized over five years. For more information, refer to our Tender Offer Statement filed with the Securities and Exchange Commission on January 12, 2016 , as amended on January 28, 2016 .

Summary of Significant Accoun25

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Basis of Accounting Presentation and Principles of Consolidation	Basis of Presentation and Principles of Consolidation
Use of Estimates	Use of Estimates
Segment Information	Segment Information Our chief operating decision maker, our CEO, reviews the financial information presented on a consolidated basis for purposes of allocating resources and evaluating our financial performance. Accordingly, we have determined that we operate in a single reportable segment, cloud-based products.
Revenue Recognition	Revenue Recognition We derive our revenue from sales of cloud-based subscription service and professional services contracts. We sell subscriptions to our cloud-based subscription service through contracts that are generally three years in length. Our cloud-based subscription service contracts do not provide customers with the right to take possession of the software supporting the cloud-based service and, as a result, are accounted for as service contracts. We commence revenue recognition for our cloud-based subscription service and professional services when all of the following criteria are met: • there is persuasive evidence of an arrangement; • the service has been provided to the customer; • collection of the fees is reasonably assured; and • the amount of fees to be paid by the customer is fixed or determinable. Our subscription and professional service arrangements do not contain refund provisions for fees earned related to services performed. We do, however, have commitments under service-level agreements, as discussed under "Warranties and Indemnification" below. Subscription Revenue. Subscription revenue recognition commences on the date that our cloud-based service is made available to the customer, which is considered the launch date, provided all of the other criteria described above are met. Revenue is recognized based on the terms in our customer contracts, which can provide for (a) a variable periodic fee based upon the actual or contractual number of users that is recognized to revenue based on the actual or contractual number of users or (b) a fixed fee that is recognized to revenue on a straight-line basis over the contractual term of the arrangement. Some of our cloud-based subscription arrangements include performance incentives that are generally based upon employee engagement. Fees for performance incentives are considered contingent revenue, and are recognized over the remaining term of the related subscription arrangement commencing at the time they are earned. Professional Services Revenue. Professional services revenue is comprised of implementation services and communication services related to our cloud-based subscription service, as well as follow-on professional services to assist our customers in further adopting our cloud-based subscription service. Nearly all of our professional services are sold on a fixed-fee basis. We do not have standalone value for our implementation services. Accordingly, we recognize implementation services revenue in the same manner as the associated cloud-based subscription service, beginning on the launch date, provided all other criteria described above have been met. For follow-on professional services that are sold separately from the cloud-based subscription service, we recognize revenue as the services are delivered. Communication services have standalone value and the associated revenue is recognized over the contractual term, generally one year, commencing when the revenue recognition criteria have been met. Multiple Deliverable Arrangements. To date, we have generated substantially all our revenue from multiple deliverable arrangements consisting of multi-year cloud-based subscription services and professional services, including implementation services and communication services. For arrangements with multiple deliverables, we evaluate whether the individual deliverables qualify as separate units of accounting. In order to treat deliverables in a multiple deliverable arrangement as separate units of accounting, the deliverables must have standalone value upon delivery. If the deliverables have standalone value upon delivery, we account for each deliverable separately and revenue is recognized for the respective deliverables as they are delivered. If one or more of the deliverables do not have standalone value upon delivery, the deliverables that do not have standalone value are generally combined with our cloud-based subscription service, and revenue for the combined unit is recognized over the remaining term of the cloud-based subscription service. Our deliverables have standalone value if we or any other vendor sells a similar service separately. We have concluded that we have standalone value for our cloud-based subscription service as we sell these services separately through renewals and for our communication services as other vendors sell similar services separately. Conversely, we have concluded that our implementation services do not have standalone value, as we and others do not yet sell these services separately. Accordingly, we consider the separate units of accounting in our multiple deliverable arrangements to be the communication services and a combined deliverable comprised of cloud-based subscription services and implementation services. When multiple deliverables included in an arrangement are separable into different units of accounting, the arrangement consideration is allocated to the identified separate units of accounting based on their relative selling price. Multiple deliverable arrangements accounting guidance provides a hierarchy to use when determining the relative selling price for each unit of accounting. Vendor-specific objective evidence, or VSOE, of selling price, based on the price at which the item is regularly sold by the vendor on a standalone basis, should be used if it exists. If VSOE of selling price is not available, third-party evidence, or TPE, of selling price is used to establish the selling price if it exists. If TPE does not exist, we estimate the best estimated selling price, or BESP. VSOE does not currently exist for any of our deliverables. Additionally, we do not believe TPE is a practical alternative due to differences in our cloud-based subscription service compared to other parties and the availability of relevant third-party pricing information for our cloud-based subscription service and our other services. Accordingly, for arrangements with multiple deliverables that can be separated into different units of accounting, we allocate the arrangement fee to the separate units of accounting based on our BESP. The amount of arrangement fee allocated is limited by contingent revenue, if any. We determine BESP for our deliverables by considering our overall pricing objectives and market conditions. This includes evaluating our pricing practices, our target prices, the size of our transactions, historical sales and our go-to-market strategy. The determination of BESP is made through consultation with and approval by management. For financial statement presentation purposes, we allocate the fees from our combined units of accounting to subscription and professional services based upon their relative selling price.
Costs of Revenue	Costs of Revenue Cost of revenue consists of the cost of subscription revenue and cost of professional services revenue. Cost of subscription revenue primarily consists of data fees, employee-related expenses (including salaries, benefits and stock-based compensation) related to hosting costs of our cloud-based service, cost of subcontractors, expenses for service delivery (which includes call center support), allocated overhead, the costs of data center capacity, amortization of internal-use software and depreciation of owned computer equipment and software. Amortization of internal-use software was $0.2 million for the year ended December 31, 2015 . Cost of professional services revenue consists primarily of employee-related expenses associated with these services, the cost of subcontractors and travel costs. The time and costs of our customer implementations vary based on the source and condition of the data we receive from third parties, the configurations that we agree to provide and the size of the customer.
Cash and Cash Equivalents	Cash and Cash Equivalents Cash and cash equivalents consist of highly liquid investments with original maturities of three months or less from the date of purchase. Our cash and cash equivalents generally consist of investments in money market funds and U.S. agency obligations. Cash and cash equivalents are stated at fair value.
Marketable Securities	Marketable Securities Our marketable securities consist of U.S. agency obligations and U.S. treasury securities, with maturities at the time of purchase of greater than three months. Marketable securities with remaining maturities in excess of one year are classified as noncurrent. We classify our marketable securities as available-for-sale at the time of purchase based on our intent and are recorded at their estimated fair value. Unrealized gains and losses for available-for-sale securities are recorded in other comprehensive loss. We evaluate our investments to assess whether those with unrealized loss positions are other than temporarily impaired. We consider impairments to be other than temporary if they are related to deterioration in credit risk or if it is likely we will sell the securities before the recovery of their cost basis. Realized gains and losses and declines in value judged to be other than temporary are determined based on the specific identification method and are reported in other income, net in the consolidated statements of operations.
Accounts Receivable and Allowance for Doubtful Accounts	Accounts Receivable and Allowance for Doubtful Accounts Accounts receivable are recorded at the invoiced amount, net of allowances for doubtful accounts. The allowance for doubtful accounts is based on our assessment of the collectability of accounts. We regularly review the adequacy of the allowance for doubtful accounts by considering the age of each outstanding invoice and the collection history of each customer to determine whether a specific allowance is appropriate. Accounts receivable deemed uncollectable are charged against the allowance for doubtful accounts when identified. For all periods presented, the allowance for doubtful accounts was not significant.
Deferred Commissions	Deferred Commissions Deferred commissions are the incremental costs that are directly associated with the noncancellable portion of cloud-based subscription service contracts with customers and consist of sales commissions paid to our direct sales force. The commissions are deferred and amortized over the noncancellable terms of the related contracts. The deferred commission amounts are recoverable through the future revenue streams under the noncancellable customer contracts. Amortization of deferred commissions is included in sales and marketing expense in the consolidated statements of operations.
Property and Equipment	Property and Equipment Property and equipment are stated at cost less accumulated depreciation. Depreciation is recorded using the straight-line method over the estimated useful lives of the respective asset as follows: Software 3–5 years Computer equipment 3 years Furniture and equipment 5–7 years Leasehold improvements Shorter of the lease term or the estimated useful lives of the improvements Maintenance and repairs are charged to expense as incurred, and improvements are capitalized. When assets are retired or otherwise disposed of, the cost and accumulated depreciation are removed from the accounts, and any resulting gain or loss is reflected in the consolidated statement of operations for the period realized.
Deferred Revenue	Deferred Revenue Deferred revenue consists of professional services and cloud-based subscription services that have been billed in advance of revenue being recognized. Additionally, deferred revenue consists of professional services that have been billed and delivered but the revenue is being deferred and recognized together with a cloud-based subscription contract as a single unit of accounting. We invoice our customers for our cloud-based subscription services based on the terms of the contract, which can be annual, quarterly or monthly installments. We invoice our customers for our professional services and the first year of communication services generally at contract execution. Deferred revenue that is anticipated to be recognized during the succeeding 12-month period is recorded as current deferred revenue, and the remaining portion is recorded as noncurrent.
Internal-use Software	Internal-use Software For our development costs related to our cloud-based service, we capitalize costs incurred during the application development stage. Costs related to preliminary project and post-implementation stages are expensed as incurred. Capitalized software development costs are included as part of property, plant and equipment and are amortized on a straight-line basis over the technology's estimated useful life, which is generally three years. The amortization expense is recorded as a component of cost of subscription revenue. We capitalized software development costs totaling $2.6 million and $0.3 million for the years ended December 31, 2015 and 2014 , respectively.
Share-based Compensation	Stock-based Compensation All stock-based compensation to employees is measured based on the grant-date fair value of the awards and recognized in our consolidated statements of operations over the period during which the employee is required to perform services in exchange for the award (generally the vesting period of the award). We estimate the fair value of stock options granted using the Black-Scholes option valuation model. For restricted stock units, fair value is based on the closing price of our Class B common stock on the grant date. Compensation expense is recognized over the vesting period of the applicable award using the straight-line method. Compensation expense for non-employee stock options and warrants is calculated using the Black-Scholes option-pricing model and is recorded as the options vest. Options subject to vesting are required to be periodically revalued over their service period, which is generally the same as the vesting period.
Income Taxes	Income Taxes We account for income taxes using the liability method, under which deferred tax assets and liabilities are determined based on the future tax consequences attributable to differences between the financial reporting carrying amounts of existing assets and liabilities and their respective tax bases and tax credit and net operating loss carryforwards. Deferred tax assets and liabilities are measured using the enacted tax rates that are expected to be in effect when the differences are expected to reverse. We assess the likelihood that deferred tax assets will be recovered from future taxable income, and a valuation allowance is established when necessary to reduce deferred tax assets to the amounts more likely than not expected to be realized. We recognize and measure uncertain tax positions using a two-step approach. The first step is to evaluate the tax position taken or expected to be taken by determining if the weight of available evidence indicates that it is more likely than not that the tax position will be sustained in an audit, including resolution of any related appeals or litigation processes. The second step is to measure the tax benefit as the largest amount that is more than 50% likely to be realized upon ultimate settlement. Significant judgment is required to evaluate uncertain tax positions. We evaluate our uncertain tax positions on a regular basis. Our evaluations are based on a number of factors, including changes in facts and circumstances, changes in tax law, correspondence with tax authorities during the course of audit and effective settlement of audit issues.
Warranties and Indemnification	Warranties and Indemnification Our cloud-based service is generally warranted to be performed in a professional manner and in a manner that will comply with the terms of the customer agreements. Our arrangements generally include certain provisions for indemnifying customers against liabilities if there is a breach of a customer’s data or if our service infringes a third party’s intellectual property rights. To date, we have not incurred any material costs as a result of such indemnifications and have not accrued any liabilities related to such obligations in the financial statements. We have entered into service-level agreements with certain customers warranting defined levels of performance and response and permitting those customers to receive credits for prepaid amounts related to subscription services in the event that we fail to meet those levels. To date, we have not experienced any significant failures to meet defined levels of performance and response as a result of those agreements. We have also agreed to indemnify our directors and executive officers for costs associated with any fees, expenses, judgments, fines and settlement amounts incurred by any of these persons in any action or proceeding to which any of those persons is, or is threatened to be, made a party by reason of the person’s service as a director or officer, including any action by us, arising out of that person’s services as our director or officer or that person’s services provided to any other company or enterprise at our request. We maintain director and officer insurance coverage that would generally enable us to recover a portion of any future amounts paid. We may also be subject to indemnification obligation by law with respect to the actions of our employees under certain circumstances and in certain jurisdictions.
Advertising Expenses	Advertising Expenses Advertising is expensed as incurred.
Concentrations of Risk and Significant Customers	Concentrations of Risk and Significant Customers Our financial instruments that are exposed to concentrations of credit risk consist primarily of cash and cash equivalents, marketable securities and accounts receivable. Although we deposit our cash with multiple financial institutions, our deposits, at times, may exceed federally insured limits. We serve our customers and users from outsourced data center facilities located in Colorado and Arizona. We have internal procedures to restore all of our production customer facing services in the event of disasters at the Colorado facility. Procedures utilizing currently deployed hardware, software and services at our disaster recovery location in Arizona allow our cloud-based service to be restored within 48 hours during the implementation of the procedures to restore services. Revenue from customers representing 10% or more of total revenue for the respective years, is summarized as follows: Year Ended December 31, 2015 2014 2013 Revenue: Customer A * 14 % 16 % * Less than 10% During the years ended December 31, 2015 , 2014 and 2013 , all of our revenue was generated by customers located in the United States. Accounts receivable from customers representing 10% or more of total accounts receivable as of the respective dates is summarized as follows: As of December 31, 2015 2014 Accounts Receivable: Customer B * 12 % Customer C 19 % 19 % * Less than 10%
Recently Issued and Adopted Accounting Pronouncements	Recently Issued and Adopted Accounting Pronouncements In November 2015, the Financial Accounting Standards Board (FASB) issued a new accounting standard that would require companies and other organizations to include lease obligations on their balance sheets. The guidance will be effective for us beginning January 1, 2019. We are evaluating the accounting, transition and disclosure requirements of the standard and cannot currently estimate the financial statement impact of adoption. At this point in time, we do not intend to adopt the standard early. In April 2015, FASB issued new accounting guidance on Customer's Accounting for Fees Paid in a Cloud Computing Arrangement. This guidance is intended to help entities evaluate the accounting for fees paid by a customer in a cloud computing arrangement, primarily to determine whether the arrangement includes a sale or license of software. The guidance will be effective for us beginning January 1, 2016. Early adoption is permitted. We have elected not to early adopt. The adoption of this guidance is not expected to have a material impact on our consolidated financial statements. In May 2014, FASB issued ASU 2014-09 regarding ASC Topic 606, Revenue from Contracts with Customers. The standard provides principles for recognizing revenue for the transfer of promised goods or services to customers with the consideration to which the entity expects to be entitled in exchange for those goods or services. In August 2015, FASB deferred the effective date of the standard for all entities by one year. The standard will become effective for the annual reporting period (including interim reporting periods) beginning after December 15, 2017, and early adoption is permitted as of annual reporting periods (including interim periods) beginning after December 15, 2016. We are evaluating the accounting, transition and disclosure requirements of the standard and cannot currently estimate the financial statement impact of adoption. At this point in time, we do not intend to adopt the standard early.

Summary of Significant Accoun26

Summary of Significant Accounting Policies Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Property, Plant and Equipment	Property and equipment are stated at cost less accumulated depreciation. Depreciation is recorded using the straight-line method over the estimated useful lives of the respective asset as follows: Software 3–5 years Computer equipment 3 years Furniture and equipment 5–7 years Leasehold improvements Shorter of the lease term or the estimated useful lives of the improvements Property and equipment consisted of the following (in thousands): As of December 31, 2015 2014 Leasehold improvements $ 2,046 $ 1,058 Computer equipment 4,345 3,247 Software 885 874 Capitalization of internal-use software 2,925 291 Furniture and equipment 853 301 Total 11,054 5,771 Accumulated depreciation (4,158 ) (2,141 ) Property and equipment, net $ 6,896 $ 3,630
Schedules of Concentration of Risk, by Risk Factor	Accounts receivable from customers representing 10% or more of total accounts receivable as of the respective dates is summarized as follows: As of December 31, 2015 2014 Accounts Receivable: Customer B * 12 % Customer C 19 % 19 % * Less than 10% Revenue from customers representing 10% or more of total revenue for the respective years, is summarized as follows: Year Ended December 31, 2015 2014 2013 Revenue: Customer A * 14 % 16 % * Less than 10%

Marketable Securities (Tables)

Marketable Securities (Tables)	12 Months Ended
	Dec. 31, 2015
Investments, Debt and Equity Securities [Abstract]
Available-for-sale Securities	At December 31, 2015 and December 31, 2014 , respectively, marketable securities consisted of the following (in thousands): Amortized Cost Unrealized Gains Unrealized Losses Fair Value December 31, 2015 U.S. agency obligations $ 83,763 $ — $ (48 ) $ 83,715 U.S. treasury securities 33,924 — (31 ) 33,893 Money market mutual funds 1,038 — — 1,038 118,725 — (79 ) 118,646 Included in cash and cash equivalents 4,038 — (1 ) 4,037 Included in marketable securities $ 101,334 $ — $ (60 ) $ 101,274 Included in marketable securities, noncurrent $ 13,353 $ — $ (18 ) $ 13,335 Amortized Cost Unrealized Gains Unrealized Losses Fair Value December 31, 2014 U.S. agency obligations $ 177,297 $ 4 $ (44 ) $ 177,257 U.S. treasury securities 5,580 1 — 5,581 Money market mutual funds 1,919 — — 1,919 184,796 5 (44 ) 184,757 Included in cash and cash equivalents 3,480 — — 3,480 Included in marketable securities $ 175,093 $ 5 $ (41 ) $ 175,057 Included in marketable securities, noncurrent $ 6,223 $ — $ (3 ) $ 6,220

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Fair Value, Assets Measured on Recurring Basis	The following tables present information about our assets that are measured at fair value on a recurring basis using the above input categories (in thousands): Level 1 Level 2 Total December 31, 2015 Cash equivalents: Money market mutual funds $ 1,038 $ — $ 1,038 U.S. agency obligations — 3,000 3,000 Marketable securities: U.S. agency obligations — 80,715 80,715 U.S. treasury securities — 33,893 33,893 $ 1,038 $ 117,608 $ 118,646 Level 1 Level 2 Total December 31, 2014 Cash equivalents: Money market mutual funds $ 1,919 $ — $ 1,919 U.S. agency obligations — 1,561 1,561 Marketable securities: U.S. agency obligations — 175,696 175,696 U.S. treasury securities — 5,581 5,581 $ 1,919 $ 182,838 $ 184,757

Prepaid Expenses and Other Cu29

Prepaid Expenses and Other Current Assets (Tables)	12 Months Ended
	Dec. 31, 2015
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Schedule of Accrued Expenses and Other Current Assets	Prepaid expenses and other current assets consisted of the following (in thousands): As of December 31, 2015 2014 Prepaid expenses and advances $ 3,033 $ 2,285 Security deposit 228 211 Interest receivable on marketable securities 361 537 Other current assets 150 443 Total $ 3,772 $ 3,476

Property and equipment, net (Ta

Property and equipment, net (Tables)	12 Months Ended
	Dec. 31, 2015
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	Property and equipment are stated at cost less accumulated depreciation. Depreciation is recorded using the straight-line method over the estimated useful lives of the respective asset as follows: Software 3–5 years Computer equipment 3 years Furniture and equipment 5–7 years Leasehold improvements Shorter of the lease term or the estimated useful lives of the improvements Property and equipment consisted of the following (in thousands): As of December 31, 2015 2014 Leasehold improvements $ 2,046 $ 1,058 Computer equipment 4,345 3,247 Software 885 874 Capitalization of internal-use software 2,925 291 Furniture and equipment 853 301 Total 11,054 5,771 Accumulated depreciation (4,158 ) (2,141 ) Property and equipment, net $ 6,896 $ 3,630

Accrued Compensation (Tables)

Accrued Compensation (Tables)	12 Months Ended
	Dec. 31, 2015
Compensation Related Costs [Abstract]
Schedule of Accrued Compensation	Accrued compensation consisted of the following (in thousands): As of December 31, 2015 2014 Accrued bonuses $ 4,034 $ 4,728 Accrued commissions 5,212 3,035 Other benefits payable 2,231 2,692 Total $ 11,477 $ 10,455

Deferred Revenue (Tables)

Deferred Revenue (Tables)	12 Months Ended
	Dec. 31, 2015
Deferred Revenue Disclosure [Abstract]
Deferred Revenue, by Arrangement, Disclosure	Deferred revenue consisted of the following (in thousands): As of December 31, 2015 2014 Subscription $ 18,029 $ 14,826 Professional services—implementation 5,254 2,974 Professional services—communications 3,307 2,908 Total current 26,590 20,708 Subscription 1,163 1,950 Professional services—implementation 5,367 4,327 Professional services—communications 992 375 Total noncurrent 7,522 6,652 Total $ 34,112 $ 27,360

Commitments and Contingencies C

Commitments and Contingencies Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Schedule of Future Minimum Rental Payments for Operating Leases	As of December 31, 2015 , the future minimum lease payments under noncancellable operating leases are as follows (in thousands): Operating Leases Contractual Obligations 2016 $ 3,369 $ 243 2017 3,073 — 2018 2,548 — 2019 2,624 — 2020 and later 3,830 — $ 15,444 $ 243
Contractual Obligation, Fiscal Year Maturity Schedule	As of December 31, 2015 , the future minimum lease payments under noncancellable operating leases are as follows (in thousands): Operating Leases Contractual Obligations 2016 $ 3,369 $ 243 2017 3,073 — 2018 2,548 — 2019 2,624 — 2020 and later 3,830 — $ 15,444 $ 243

Stockholders' Equity (Deficit)

Stockholders' Equity (Deficit) (Tables)	12 Months Ended
	Dec. 31, 2015
Equity and Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value	Options Outstanding Number of Shares Outstanding Weighted- Average Exercise Price Weighted- Average Remaining Contractual Life in Years Aggregate Intrinsic Value Balance at December 31, 2014 16,392,539 $ 4.40 7.3 $ 128,541 Stock options granted 491,900 $ 8.95 Stock options exercised (4,177,555 ) $ 1.02 Stock options canceled and forfeited (3,145,171 ) $ 5.87 Balance at December 31, 2015 9,561,713 $ 5.62 6.9 $ 16,694 Vested or expected to vest December 31, 2015 9,022,878 $ 5.50 6.8 $ 16,149 Exercisable as of December 31, 2015 5,416,829 $ 3.99 6.0 $ 12,497
Nonvested Restricted Stock Shares Activity	The following table summarizes activities for RSUs: Restricted Stock Units Outstanding Number of shares Weighted Average Grant-Date Fair Value Balance at December 31, 2014 1,398,893 $ 11.06 Restricted stock units granted 6,507,250 $ 7.24 Restricted stock units vested (295,468 ) $ 10.70 Restricted stock units canceled and forfeited (925,557 ) $ 9.06 Balance at December 31, 2015 6,685,118 $ 7.63
Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions	The fair value of each option grant was estimated on the date of grant using the Black-Scholes option-valuation model with the following assumptions and fair value per share: Year Ended December 31, 2015 2014 2013 Volatility 53% 60% 57.8%-60% Expected life (in years) 6.2 5.0-6.3 5.0-7.2 Risk-free interest rate 1.38%-1.91% 1.53%-2.05% 0.7%-1.8% Dividend yield —% —% —% Weighted-average fair value of underlying common stock $8.95 $14.74 $3.02

Income Taxes Income Taxes (Tabl

Income Taxes Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Schedule of Income before Income Tax	The components of loss from continuing operations before income taxes were generated solely in the United States as follows (in thousands): Year Ended December 31, 2015 2014 2013 United States $ (79,920 ) $ (85,940 ) $ (62,182 )
Schedule of Effective Income Tax Rate Reconciliation	Reconciliations of the statutory federal income tax rate and our effective tax rate consist of the following (in thousands): Year Ended December 31, 2015 2014 2013 Tax at federal statutory rate $ (27,173 ) $ (29,220 ) $ (21,142 ) State statutory rate (net of federal benefit) (1,560 ) (1,728 ) (1,921 ) Non-deductible stock compensation 2,334 (19 ) 619 Change in valuation allowance 24,332 30,571 22,184 Other 2,067 396 260 $ — $ — $ —
Schedule of Deferred Tax Assets and Liabilities	Significant components of our deferred tax assets and liabilities were as follows (in thousands): As of December 31, Deferred tax assets: 2015 2014 Net operating loss carryforwards $ 93,165 $ 72,984 Deferred rent 235 127 Accrued bonus — 68 Accrued compensation 326 539 Stock-based compensation 6,224 3,266 Other reserves and accruals 4 2 Property and equipment 322 16 Deferred revenue 3,017 2,173 103,293 79,175 Valuation allowance (103,293 ) (79,175 ) Net deferred tax assets $ — $ —
Schedule of Unrecognized Tax Benefits Roll Forward	A reconciliation of the beginning and ending amount of the gross unrecognized tax benefit is as follows (in thousands): Year Ended December 31, 2015 2014 2013 Gross unrecognized tax benefits at the beginning of the year $ 7,214 $ 4,513 $ 2,445 Increases for tax positions of prior years 133 871 — Decreases for tax positions of prior years (346 ) (831 ) — Increases for tax positions related to the current year 2,539 2,661 2,068 Gross unrecognized tax benefits at the end of the year $ 9,540 $ 7,214 $ 4,513

Net Loss per Share (Tables)

Net Loss per Share (Tables)	12 Months Ended
	Dec. 31, 2015
Earnings Per Share [Abstract]
Schedule of Earnings Per Share, Basic and Diluted	The following table presents the calculation of basic and diluted net loss per share for our common stock (in thousands, except per share data): Year Ended December 31, 2015 2014 2013 Class A Class B Class A Class B Class A Net loss $ (48,116 ) $ (31,804 ) $ (67,655 ) $ (18,285 ) $ (62,182 ) Weighted-average shares used to compute basic and diluted net loss per share 56,444 37,309 58,555 15,826 9,895 Basic and diluted net loss per share $ (0.85 ) $ (0.85 ) $ (1.16 ) $ (1.16 ) $ (6.28 )
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share	The following securities were excluded from the calculation of diluted net loss per share for common stock because their effect would have been anti-dilutive for the periods presented (in thousands): Year Ended December 31, 2015 2014 2013 Convertible preferred stock — — 64,476 Stock options and restricted common stock 16,247 17,791 16,687 Warrants 115 115 175 $ 16,362 $ 17,906 $ 81,338

Selected Quarterly Financial 37

Selected Quarterly Financial Data (unaudited) (Tables)	12 Months Ended
	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Schedule of Quarterly Financial Information	The following tables set forth selected unaudited quarterly consolidated statements of operations data for each of the eight quarters in years 2015 and 2014 (in thousands, except per share data): Quarter Ended Mar 31, Jun 30, Sept 30, Dec 31, Mar 31, Jun 30, Sept 30, Dec 31, Total revenue 8,376 10,533 12,209 14,487 15,951 18,510 19,539 21,315 Gross profit 1,793 3,116 5,054 7,870 8,779 10,256 10,852 11,660 Net loss $ (24,281 ) $ (21,776 ) $ (20,199 ) $ (19,684 ) $ (19,643 ) $ (21,212 ) $ (20,007 ) $ (19,058 ) Net loss per share, basic and diluted $ (0.90 ) $ (0.24 ) $ (0.23 ) $ (0.22 ) $ (0.21 ) $ (0.23 ) $ (0.21 ) $ (0.20 )

Organization and Description 38

Organization and Description of Business (Details) - USD ($) $ / shares in Units, $ in Thousands, shares in Millions	Mar. 19, 2014	Mar. 19, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Class of Stock [Line Items]
Stock Issued During Period, Value, New Issues				$ 185,628
Proceeds from Issuance Initial Public Offering			$ 0	$ 189,943	$ 0
IPO [Member]
Class of Stock [Line Items]
Stock Issued During Period, Value, New Issues		$ 204,200
Proceeds from Issuance Initial Public Offering		185,600
Payments of Stock Issuance Costs, Underwriter Fees and Commissions		14,300
Deferred Offering Costs	$ 4,300	$ 4,300
IPO [Member] | Class B [Member]
Class of Stock [Line Items]
Stock Issued During Period, Shares, New Issues	12.8	12.8
Shares Issued, Price Per Share	$ 16	$ 16

Summary of Significant Accoun39

Summary of Significant Accounting Policies (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Capitalized computer software, amortization	$ 0.2
Capitalized software costs	2.6	$ 0.3
Advertising expense	$ 0.4	$ 0.7	$ 0.4
Cloud-Based Subscription Service [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Contractual term of services (in years)	3 years
Communication Services [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Contractual term of services (in years)	1 year

Summary of Significant Accoun40

Summary of Significant Accounting Policies - Schedule of Estimated Useful Life of Property and Equipment (Details)	12 Months Ended
	Dec. 31, 2015
Software Development [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	3 years
Software Development [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	5 years
Computer Equipment [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	3 years
Furniture and Equipment [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	5 years
Furniture and Equipment [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life	7 years

Summary of Significant Accoun41

Summary of Significant Accounting Policies - Summary of Revenue by Major Customers (Details)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Customer A [Member] | Customer Concentration Risk [Member] | Revenue [Member]
Concentration Risk [Line Items]
Concentration Risk, Percentage	14.00%	16.00%

Summary of Significant Accoun42

Summary of Significant Accounting Policies - Summary of Accounts Receivable by Major Customers (Details) - Accounts Receivable [Member] - Customer Concentration Risk [Member]	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Customer A [Member]
Concentration Risk [Line Items]
Concentration Risk, Percentage		12.00%
Customer C [Member]
Concentration Risk [Line Items]
Concentration Risk, Percentage	19.00%	19.00%

Marketable Securities (Details)

Marketable Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 118,725	$ 184,796
Unrealized Gains	0	5
Unrealized Losses	(79)	(44)
Fair Value	118,646	184,757
Included in cash and cash equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	4,038	3,480
Unrealized Gains	0	0
Unrealized Losses	(1)	0
Fair Value	4,037	3,480
Included in marketable securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	101,334	175,093
Unrealized Gains	0	5
Unrealized Losses	(60)	(41)
Fair Value	101,274	175,057
Included in marketable securities, noncurrent [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	13,353	6,223
Unrealized Gains	0	0
Unrealized Losses	(18)	(3)
Fair Value	13,335	6,220
U.S. agency obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	83,763	177,297
Unrealized Gains	0	4
Unrealized Losses	(48)	(44)
Fair Value	83,715	177,257
U.S. treasury securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	33,924	5,580
Unrealized Gains	0	1
Unrealized Losses	(31)	0
Fair Value	33,893	5,581
Money market mutual funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,038	1,919
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	$ 1,038	$ 1,919

Fair Value Measurements (Detail

Fair Value Measurements (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Gross Realized Gain (Loss)	$ 0	$ 0
Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Maturity Period	1 year
Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Maturity Period	5 years

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Assets Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Marketable securities:
Marketable securities	$ 118,646	$ 184,757
Money market mutual funds [Member]
Marketable securities:
Marketable securities	1,038	1,919
U.S. agency obligations [Member]
Marketable securities:
Marketable securities	83,715	177,257
U.S. treasury securities [Member]
Marketable securities:
Marketable securities	33,893	5,581
Fair Value, Measurements, Recurring
Marketable securities:
Assets, Fair Value Disclosure	118,646	184,757
Fair Value, Measurements, Recurring | Money market mutual funds [Member]
Cash equivalents:
Cash equivalents	1,038	1,919
Fair Value, Measurements, Recurring | U.S. agency obligations [Member]
Cash equivalents:
Cash equivalents	3,000	1,561
Marketable securities:
Marketable securities	80,715	175,696
Fair Value, Measurements, Recurring | U.S. treasury securities [Member]
Marketable securities:
Marketable securities	33,893	5,581
Fair Value, Measurements, Recurring | Level 1 [Member]
Marketable securities:
Assets, Fair Value Disclosure	1,038	1,919
Fair Value, Measurements, Recurring | Level 1 [Member] | Money market mutual funds [Member]
Cash equivalents:
Cash equivalents	1,038	1,919
Fair Value, Measurements, Recurring | Level 1 [Member] | U.S. agency obligations [Member]
Cash equivalents:
Cash equivalents	0	0
Marketable securities:
Marketable securities	0	0
Fair Value, Measurements, Recurring | Level 1 [Member] | U.S. treasury securities [Member]
Marketable securities:
Marketable securities	0	0
Fair Value, Measurements, Recurring | Level 2 [Member]
Marketable securities:
Assets, Fair Value Disclosure	117,608	182,838
Fair Value, Measurements, Recurring | Level 2 [Member] | Money market mutual funds [Member]
Cash equivalents:
Cash equivalents	0	0
Fair Value, Measurements, Recurring | Level 2 [Member] | U.S. agency obligations [Member]
Cash equivalents:
Cash equivalents	3,000	1,561
Marketable securities:
Marketable securities	80,715	175,696
Fair Value, Measurements, Recurring | Level 2 [Member] | U.S. treasury securities [Member]
Marketable securities:
Marketable securities	$ 33,893	$ 5,581

Prepaid Expenses and Other Cu46

Prepaid Expenses and Other Current Assets - Schedule of Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Prepaid expenses and advances	$ 3,033	$ 2,285
Security deposit	228	211
Interest receivable on marketable securities	361	537
Other current assets	150	443
Total	$ 3,772	$ 3,476

Property and equipment, net (De

Property and equipment, net (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Property, Plant and Equipment [Abstract]
Depreciation Expense	$ 2	$ 1.4	$ 0.6

Property and equipment, net - S

Property and equipment, net - Schedule of Property, Plant and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Property and Equipment	$ 11,054	$ 5,771
Capitalization of internal-use software	2,925	291
Accumulated depreciation	(4,158)	(2,141)
Property and equipment, net	6,896	3,630
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and Equipment	2,046	1,058
Computer Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and Equipment	4,345	3,247
Software [Member]
Property, Plant and Equipment [Line Items]
Property and Equipment	885	874
Furniture and Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and Equipment	$ 853	$ 301

Related Party Transactions (Det

Related Party Transactions (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Related Party Transaction [Line Items]
Payments to Acquire Interest in Subsidiaries and Affiliates	$ 4,125	$ 0	$ 0
Lyra Health [Member]
Related Party Transaction [Line Items]
Payments to Acquire Interest in Subsidiaries and Affiliates	4,100
Second Investment [Member]
Related Party Transaction [Line Items]
Payments to Acquire Interest in Subsidiaries and Affiliates	1,000
Initial Investment [Member]
Related Party Transaction [Line Items]
Payments to Acquire Interest in Subsidiaries and Affiliates	$ 3,100

Accrued Compensation - Schedule

Accrued Compensation - Schedule of Accrued Compensation (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Compensation Related Costs [Abstract]
Accrued bonuses	$ 4,034	$ 4,728
Accrued Sales Commission, Current	5,212	3,035
Other benefits payable	2,231	2,692
Total	$ 11,477	$ 10,455

Deferred Revenue - Components o

Deferred Revenue - Components of Deferred Revenue (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Deferred Revenue Arrangement [Line Items]
Total current	$ 26,590	$ 20,708
Total noncurrent	7,522	6,652
Total	34,112	27,360
Subscription [Member]
Deferred Revenue Arrangement [Line Items]
Total current	18,029	14,826
Total noncurrent	1,163	1,950
Professional Services - Implementation [Member]
Deferred Revenue Arrangement [Line Items]
Total current	5,254	2,974
Total noncurrent	5,367	4,327
Professional Services - Communications [Member]
Deferred Revenue Arrangement [Line Items]
Total current	3,307	2,908
Total noncurrent	$ 992	$ 375

Commitments and Contingencies -

Commitments and Contingencies - Schedule of Future Operating Lease Payments and Contractual Obligations (Details) $ in Thousands	Dec. 31, 2015USD ($)
Operating Leases
2,015	$ 3,369
2,016	3,073
2,017	2,548
2,018	2,624
2019 and later	3,830
Total	15,444
Contractual Obligations
2,015	243
2,016	0
2,017	0
2,018	0
2019 and later	0
Total	$ 243

Commitments and Contingencies (

Commitments and Contingencies (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Commitments and Contingencies Disclosure [Abstract]
Rent expense	$ 1	$ 1.2	$ 2.1

Stockholders' Equity (Deficit54

Stockholders' Equity (Deficit) Stockholders' Equity (Deficit) - Initial Public Offering (Details) - IPO [Member] - Class B [Member] shares in Millions	Mar. 19, 2014$ / sharesshares	Mar. 19, 2014$ / sharesshares
Class of Stock [Line Items]
Issuance of common stock upon initial public offering, net of issuance costs (in shares) | shares	12.8	12.8
Share price (in dollars per share) | $ / shares	$ 16	$ 16

Stockholders' Equity (Deficit55

Stockholders' Equity (Deficit) - Schedule of Stock Option Grants (Details) - Stock Option [Member] - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Options Outstanding
Beginning Balance	16,392,539
Stock option grants	491,900
Stock options exercised	4,177,555
Stock options canceled	3,145,171
Ending Balance	9,561,713	16,392,539
Vested or expected to vest December 31, 2015	9,022,878
Exercisable as of December 31, 2015	5,416,829,000
Weighted- Average Exercise Price
Beginning Balance	$ 4.40
Stock option grants	8.95
Stock options exercised	1.02
Stock options canceled	5,870
Ending Balance	5.62	$ 4.40
Vested or expected to vest, weighted average exercise price	5.50
Exercisable, weighted average share price	$ 3,990
Weighted- Average Remaining Contractual Life in Years	6 years 10 months 25 days	7 years 3 months 19 days
Vested or expected to vest, weighted average remaining contractual life in years	6 years 9 months 18 days
Exercisable, weighted average remaining contractual life in years	6 years
Aggregate Intrinsic Value
Aggregate Intrinsic Value	$ 16,694	$ 128,541
Vested or expected to vest, aggregate intrinsic value	16,149
Exercisable as of December 31, 2015	$ 12,497

Stockholders' Equity (Deficit56

Stockholders' Equity (Deficit) - Stock Options Activity and Stock-based Compensation (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock granted value, share-based compensation, gross	$ 2.5	$ 39.9	$ 17
Total grant-date fair value of awards vested	10.8	9.7	1.7
Total intrinsic value of options exercised	25.3	31.1	$ 1.8
Unrecognized compensation costs on non-vested stock options	19
Capitalized amount	$ 0.3
Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Period of recognition for unrecognized compensation costs (in years)	2 years 4 months 24 days
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock granted value, share-based compensation, gross	$ 47.1	$ 15.7
Period of recognition for unrecognized compensation costs (in years)	2 years 3 months 18 days
Vested in period, fair value	$ (3.2)
Unrecognized compensation costs on non-vested restricted stock units	$ 43.6

Stockholders' Equity (Deficit)-

Stockholders' Equity (Deficit)- Restrict Stock Unit Activity (Details) - Restricted Stock Units (RSUs) [Member] - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning Balance (in shares)	1,398,893
Restricted stock units granted (in shares)	6,507,250
Restricted stock units vested (in shares)	(295,468)
Restricted stock units canceled and forfeited (in shares)	(925,557)
Ending Balance (in shares)	6,685,118
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Balance (in dollars per share)	$ 7.63	$ 11,060
Restricted stock units granted (in dollars per share)	7.24
Restricted stock units vested (in dollars per share)	10,700
Restricted stock units canceled and forfeited (in dollars per share)	$ 9.06

Stockholders' Equity (Deficit58

Stockholders' Equity (Deficit) - Assumptions Related to Share-based Compensation (Details) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants in period, weighted average grant date fair value	$ 8.95	$ 14.74	$ 3.02
Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Volatility	53.00%	60.00%
Expected life (in years)	6 years 2 months 1 day
Risk-free interest rate, minimum	1.38%	1.53%	0.70%
Risk-free interest rate, maximum	1.91%	2.05%	1.80%
Dividend yield	0.00%	0.00%	0.00%
Minimum [Member] | Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Volatility			58.00%
Expected life (in years)		5 years	5 years
Maximum [Member] | Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Volatility			60.00%
Expected life (in years)		6 years 3 months 18 days	7 years 2 months 12 days

Stockholders' Equity (Deficit59

Stockholders' Equity (Deficit) - Warrants (Details) - USD ($) $ / shares in Units, $ in Thousands	Dec. 11, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Class of Warrant or Right [Line Items]
Expense related to warrant		$ 0	$ 2,639	$ 135
Class A [Member]
Class of Warrant or Right [Line Items]
Number of securities called by warrant (in shares)	175,000
Exercise price of warrants (in dollars per share)	$ 5
Class of warrant term (in years)	10 years
Expense related to warrant			$ 2,600

Income Taxes - Components of Lo

Income Taxes - Components of Loss from Continuing Operations before Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
United States	$ (19,058)	$ (20,007)	$ (21,212)	$ (19,643)	$ (19,684)	$ (20,199)	$ (21,776)	$ (24,281)	$ (79,920)	$ (85,940)	$ (62,182)

Income Taxes - Schedule of Effe

Income Taxes - Schedule of Effective Income Tax Rate Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Tax at federal statutory rate	$ (27,173)	$ (29,220)	$ (21,142)
State statutory rate (net of federal benefit)	(1,560)	(1,728)	(1,921)
Non-deductible stock compensation	2,334	(19)	619
Change in valuation allowance	24,332	30,571	22,184
Other	2,067	396	260
Income Tax Expense (Benefit)	$ 0	$ 0	$ 0

Income Taxes - Components of De

Income Taxes - Components of Deferred Tax Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Deferred tax assets:
Net operating loss carryforwards	$ 93,165	$ 72,984
Deferred rent	235	127
Accrued bonus	0	68
Accrued compensation	326	539
Stock-based compensation	6,224	3,266
Other reserves and accruals	4	2
Property and equipment	322	16
Deferred revenue	3,017	2,173
Deferred Tax Assets, Gross	103,293	79,175
Valuation allowance	(103,293)	(79,175)
Net deferred tax assets	$ 0	$ 0

Income Taxes (Details)

Income Taxes (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Tax Credit Carryforward [Line Items]
Increase in valuation allowance	$ 30,600,000	$ 24,100,000
Tax benefits related to stock-based compensation	0	$ 0
Operating loss carryforwards, federal	250,000,000
Operating loss carryforwards, state	155,200,000
Effective tax rate		0.00%
Research and Development Tax Credit Carryforward [Member] | Federal [Member]
Tax Credit Carryforward [Line Items]
Tax credit carryforwards	4,500,000
Research and Development Tax Credit Carryforward [Member] | California [Member]
Tax Credit Carryforward [Line Items]
Tax credit carryforwards	$ 5,100,000

Income Taxes - Roll Forward of

Income Taxes - Roll Forward of Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Gross unrecognized tax benefits at the beginning of the year	$ 7,214	$ 4,513	$ 2,445
Increases for tax positions of prior years	133	871	0
Decreases for tax positions of prior years	(346)	(831)	0
Increases for tax positions related to the current year	2,539	2,661	2,068
Gross unrecognized tax benefits at the end of the year	$ 9,540	$ 7,214	$ 4,513

Net Loss per Share - Calculatio

Net Loss per Share - Calculation of Basic and Diluted EPS for Common Stock (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Schedule of Earnings Per Share, Basic and Diluted, by Common Class, Including Two Class Method [Table] [Line Items]
Net loss	$ (19,058)	$ (20,007)	$ (21,212)	$ (19,643)	$ (19,684)	$ (20,199)	$ (21,776)	$ (24,281)	$ (79,920)	$ (85,940)	$ (62,182)
Weighted-average shares used to compute basic and diluted net loss per share									93,753	74,381	9,895
Basic and diluted net loss per share (in usd per share)	$ (0.20)	$ (0.21)	$ (0.23)	$ (0.21)	$ (0.22)	$ (0.23)	$ (0.24)	$ (0.90)	$ (0.85)	$ (1.16)	$ (6.28)
Class A [Member]
Schedule of Earnings Per Share, Basic and Diluted, by Common Class, Including Two Class Method [Table] [Line Items]
Net loss									$ (48,116)	$ (67,655)	$ (62,182)
Weighted-average shares used to compute basic and diluted net loss per share									56,444	58,555	9,895
Basic and diluted net loss per share (in usd per share)									$ (0.85)	$ (1.16)	$ (6.28)
Class B [Member]
Schedule of Earnings Per Share, Basic and Diluted, by Common Class, Including Two Class Method [Table] [Line Items]
Net loss									$ (31,804)	$ (18,285)
Weighted-average shares used to compute basic and diluted net loss per share									37,309	15,826
Basic and diluted net loss per share (in usd per share)									$ (0.85)	$ (1.16)

Net Loss per Share - Summary of

Net Loss per Share - Summary of Antidilutive Securities (Details) - Class A [Member] - shares shares in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	16,362	17,906	81,338
Convertible Preferred Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	0	0	64,476
Stock Options and Restricted Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	16,247	17,791	16,687
Warrants [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	115	115	175

401(k) Plan 401(k) Plan (Detail

401(k) Plan 401(k) Plan (Details) - 401(k) Plan [Member] $ in Millions	12 Months Ended
	Dec. 31, 2015USD ($)
Defined Contribution Plan Disclosure [Line Items]
Maximum annual contributions per employee, percent (up to)	100.00%
Defined contribution plan, cost recognized	$ 0.9

Selected Quarterly Financial 68

Selected Quarterly Financial Data (unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Quarterly Financial Information Disclosure [Abstract]
Total revenue	$ 21,315	$ 19,539	$ 18,510	$ 15,951	$ 14,487	$ 12,209	$ 10,533	$ 8,376	$ 75,315	$ 45,605	$ 12,973
Gross profit	11,660	10,852	10,256	8,779	7,870	5,054	3,116	1,793	41,547	17,833	(4,331)
Net loss	$ (19,058)	$ (20,007)	$ (21,212)	$ (19,643)	$ (19,684)	$ (20,199)	$ (21,776)	$ (24,281)	$ (79,920)	$ (85,940)	$ (62,182)
Net loss per share, basic and diluted	$ (0.20)	$ (0.21)	$ (0.23)	$ (0.21)	$ (0.22)	$ (0.23)	$ (0.24)	$ (0.90)	$ (0.85)	$ (1.16)	$ (6.28)

Subsequent Events (Details)

Subsequent Events (Details) - Subsequent Event [Member] $ / shares in Units, $ in Millions	Feb. 24, 2016USD ($)installmentemployee$ / sharesshares	Jan. 12, 2016$ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average exercise price of options tendered (in dollars per share)	$ 11.03
Incremental expense | $	$ 1.8
Old Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Conversion ratio		1
New Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period (in years)	5 years
Number of monthly installments | installment	60
Class B [Member] | Old Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share price threshold (in dollars per share)		$ 6.76
Class B [Member] | New Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average exercise price of options tendered (in dollars per share)	$ 2.99
Common Class A and Class B [Member] | Old Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of employees eligible to tender | employee	132
Number of options eligible for offer | shares	2,881,013
Number of employees tendered | employee	108
Common Class A and Class B [Member] | New Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of options tendered | shares	2,685,396