Castlight Health (CSLT) 10-Q 31 Jul 20 2020 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2020	Jul. 27, 2020
Document Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2020
Document Transition Report	false
Entity File Number	001-36330
Entity Registrant Name	CASTLIGHT HEALTH, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	26-1989091
Entity Address, Address Line One	150 Spear Street
Entity Address, Address Line Two	Suite 400
Entity Address, City or Town	San Francisco
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94105
City Area Code	415
Local Phone Number	829-1400
Title of 12(b) Security	Class B Common Stock, par value $0.0001 per share
Trading Symbol	CSLT
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Amendment Flag	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q2
Entity Central Index Key	0001433714
Current Fiscal Year End Date	--12-31
Class A common stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		35,028,171
Class B
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		115,602,861

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 44,274	$ 43,017
Marketable securities	0	16,411
Accounts receivable and other, net	33,175	31,397
Prepaid expenses and other current assets	5,643	4,645
Total current assets	83,092	95,470
Property and equipment, net	6,353	4,856
Restricted cash, non-current	1,144	1,144
Deferred commissions	11,719	14,718
Deferred professional service costs	5,717	6,711
Intangible assets, net	10,046	12,178
Goodwill	41,485	91,785
Operating lease right-of-use assets, net	11,122	13,906
Other assets	1,595	2,016
Total assets	172,273	242,784
Current liabilities:
Accounts payable	8,606	19,596
Accrued expenses and other current liabilities	8,887	10,454
Accrued compensation	5,656	8,770
Deferred revenue	12,930	10,173
Operating lease liabilities	5,429	5,914
Total current liabilities	41,508	54,907
Deferred revenue, non-current	577	572
Debt, non-current	465	1,395
Operating lease liabilities, non-current	9,290	11,823
Other liabilities, non-current	1,269	1,213
Total liabilities	53,109	69,910
Commitments and contingencies
Stockholders’ equity:
Additional paid-in capital	634,730	627,899
Accumulated other comprehensive income	0	2
Accumulated deficit	(515,581)	(455,042)
Total stockholders’ equity	119,164	172,874
Total liabilities and stockholders’ equity	172,273	242,784
Class A common stock
Stockholders’ equity:
Common stock	4	4
Class B common stock
Stockholders’ equity:
Common stock	$ 11	$ 11

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Jun. 30, 2020	Dec. 31, 2019
Class A common stock
Par value (usd per share)	$ 0.0001	$ 0.0001
Common stock authorized (in shares)	200,000,000	200,000,000
Common stock issued (in shares)	35,028,171	35,032,053
Common stock outstanding (in shares)	35,028,171	35,032,053
Class B
Par value (usd per share)	$ 0.0001	$ 0.0001
Common stock authorized (in shares)	800,000,000	800,000,000
Common stock issued (in shares)	115,598,256	113,177,162
Common stock outstanding (in shares)	115,598,256	113,177,162

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Revenue:
Total revenue, net		$ 35,500	$ 35,910	$ 74,545	$ 71,400
Cost of revenue:
Total cost of revenue		12,761	14,163	27,234	28,273
Gross profit		22,739	21,747	47,311	43,127
Operating expenses:
Sales and marketing	[1]	7,683	8,889	18,155	18,104
Research and development	[1]	13,043	14,487	26,865	30,212
General and administrative	[1]	6,340	7,010	12,916	14,303
Goodwill impairment		0	0	50,300	0
Total operating expenses		27,066	30,386	108,236	62,619
Operating loss		(4,327)	(8,639)	(60,925)	(19,492)
Other income, net		123	258	386	572
Net loss		$ (4,204)	$ (8,381)	$ (60,539)	$ (18,920)
Net loss per share, basic and diluted (in usd per share)		$ (0.03)	$ (0.06)	$ (0.41)	$ (0.13)
Weighted-average shares used to compute basic and diluted net loss per share (in shares)		150,078	144,572	149,475	143,790
Subscription
Revenue:
Total revenue, net		$ 34,289	$ 33,964	$ 72,672	$ 67,770
Cost of revenue:
Total cost of revenue	[1]	8,819	8,234	19,051	16,400
Professional services and other
Revenue:
Total revenue, net		1,211	1,946	1,873	3,630
Cost of revenue:
Total cost of revenue	[1]	$ 3,942	$ 5,929	$ 8,183	$ 11,873
[1]	Includes stock-based compensation expense as follows: Three Months Ended June 30, Six Months Ended June 30, 2020 2019 2020 2019 Cost of revenue: Cost of subscription $ 205 $ 196 $ 374 $ 415 Cost of professional services and other 144 236 260 501 Sales and marketing 748 662 1,420 1,289 Research and development 1,314 1,733 2,477 3,437 General and administrative 858 2,030 1,924 3,192

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Subscription
Stock-based compensation expense	$ 205	$ 196	$ 374	$ 415
Professional services and other
Stock-based compensation expense	144	236	260	501
Sales and marketing
Stock-based compensation expense	748	662	1,420	1,289
Research and development
Stock-based compensation expense	1,314	1,733	2,477	3,437
General and administrative
Stock-based compensation expense	$ 858	$ 2,030	$ 1,924	$ 3,192

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Statement of Comprehensive Income [Abstract]
Net loss	$ (4,204)	$ (8,381)	$ (60,539)	$ (18,920)
Other comprehensive income (loss):
Net change in unrealized gain (loss) on available-for-sale marketable securities	(13)	7	(2)	7
Other comprehensive income (loss)	(13)	7	(2)	7
Comprehensive loss	$ (4,217)	$ (8,374)	$ (60,541)	$ (18,913)

CONDENSED CONSOLIDATED STATEM_4

CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Class A and B Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2018		141,927,205
Beginning balance at Dec. 31, 2018	$ 194,671	$ 14	$ 609,697	$ 0	$ (415,040)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Vesting of restricted stock units (in shares)		2,090,898
Exercise of stock options, net (in shares)		1,180,784
Issuance of common stock upon exercise of stock options	1,845		1,845
Stock-based compensation	8,907		8,907
Comprehensive loss	(18,913)			7	(18,920)
Ending balance (in shares) at Jun. 30, 2019		145,198,887
Ending balance at Jun. 30, 2019	186,510	$ 14	620,449	7	(433,960)
Beginning balance (in shares) at Mar. 31, 2019		143,955,787
Beginning balance at Mar. 31, 2019	189,829	$ 14	615,394	0	(425,579)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Vesting of restricted stock units (in shares)		1,123,186
Exercise of stock options, net (in shares)		119,914
Issuance of common stock upon exercise of stock options	165		165
Stock-based compensation	4,890		4,890
Comprehensive loss	(8,374)			7	(8,381)
Ending balance (in shares) at Jun. 30, 2019		145,198,887
Ending balance at Jun. 30, 2019	186,510	$ 14	620,449	7	(433,960)
Beginning balance (in shares) at Dec. 31, 2019		148,209,215
Beginning balance at Dec. 31, 2019	$ 172,874	$ 15	627,899	2	(455,042)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Vesting of restricted stock units (in shares)		2,032,476
Exercise of stock options, net (in shares)	142,729	142,729
Issuance of common stock upon exercise of stock options	$ 155		155
Issuance of common stock under the ESPP (in shares)		242,007
Issuance of common stock under the ESPP	186		186
Stock-based compensation	6,490		6,490
Comprehensive loss	(60,541)			(2)	(60,539)
Ending balance (in shares) at Jun. 30, 2020		150,626,427
Ending balance at Jun. 30, 2020	119,164	$ 15	634,730	0	(515,581)
Beginning balance (in shares) at Mar. 31, 2020		149,517,644
Beginning balance at Mar. 31, 2020	120,096	$ 15	631,445	13	(511,377)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Vesting of restricted stock units (in shares)		1,108,783
Issuance of common stock upon exercise of stock options	0
Issuance of common stock under the ESPP	0
Stock-based compensation	3,285		3,285
Comprehensive loss	(4,217)			(13)	(4,204)
Ending balance (in shares) at Jun. 30, 2020		150,626,427
Ending balance at Jun. 30, 2020	$ 119,164	$ 15	$ 634,730	$ 0	$ (515,581)

CONDENSED CONSOLIDATED STATEM_5

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Operating activities:
Net loss	$ (60,539)	$ (18,920)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	3,144	2,687
Goodwill impairment	50,300	0
Stock-based compensation	6,455	8,834
Amortization and impairment of deferred commissions	3,919	4,856
Amortization and impairment of deferred professional service costs	1,657	2,014
Non-cash operating lease expense	2,631	2,580
Accretion and amortization of marketable securities	2	(213)
Changes in operating assets and liabilities:
Accounts receivable and other, net	(1,778)	(5,795)
Deferred commissions	(920)	(2,670)
Deferred professional service costs	(629)	(901)
Prepaid expenses and other assets	(824)	(1,864)
Accounts payable	(10,201)	1,864
Operating lease liabilities	(2,616)	(2,795)
Accrued expenses and other liabilities	(1,511)	(3,131)
Deferred revenue	2,762	312
Accrued compensation	(3,114)	(806)
Net cash used in operating activities	(11,262)	(13,948)
Investing activities:
Purchase of property and equipment	(3,299)	(593)
Purchase of marketable securities	(2,994)	(13,780)
Sales of marketable securities	2,001	0
Maturities of marketable securities	17,400	11,453
Net cash provided by (used in) investing activities	13,108	(2,920)
Financing activities:
Proceeds from exercise of stock options	155	1,845
Proceeds from ESPP offering	186	0
Principal payments on long-term debt	(930)	(930)
Net cash (used in) provided by financing activities	(589)	915
Net increase (decrease) in cash, cash equivalents and restricted cash	1,257	(15,953)
Cash, cash equivalents and restricted cash at beginning of period	44,342	67,330
Cash, cash equivalents and restricted cash at end of period	45,599	51,377
Reconciliation of cash, cash equivalents and restricted cash:
Total cash, cash equivalents and restricted cash	$ 45,599	$ 51,377

Organization and Description of

Organization and Description of Business	6 Months Ended
	Jun. 30, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Description of Business	Organization and Description of Business Castlight Health, Inc. (“Castlight” or “the Company”) provides health navigation solutions for large U.S. employers and health plans (“customers”) and their respective employees and members (“users”). Castlight’s offerings deliver a personalized and simplified user experience that helps connect individuals with the right provider or available benefit at the right time. Castlight’s navigation offerings have demonstrated measurable results, driving increased levels of user satisfaction and program utilization and lower healthcare costs for its customers and millions of users. The Company was incorporated in the State of Delaware in January 2008. The Company's principal executive offices are located in San Francisco, California.

Accounting Standards and Signif

Accounting Standards and Significant Accounting Policies	6 Months Ended
	Jun. 30, 2020
Accounting Policies [Abstract]
Accounting Standards and Significant Accounting Policies	Accounting Standards and Significant Accounting Policies Basis of Presentation and Principles of Consolidation The accompanying unaudited condensed consolidated financial statements include Castlight and its wholly-owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) and applicable rules and regulations of the Securities and Exchange Commission (“SEC”) regarding interim financial reporting. 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, stockholders’ equity and cash flows. The results for the interim periods presented are not necessarily indicative of the results expected for any future period. The following information should be read in conjunction with the audited financial statements and notes thereto included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019. Other than as described below, there have been no changes to the Company's significant accounting policies described in the Company's Annual Report that have had a material impact on the Company's consolidated financial statements and related notes. Use of Estimates The preparation of condensed consolidated financial statements in conformity with GAAP requires the Company 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: • Variable consideration included in the transaction price of the Company’s contracts with customers; • The standalone selling price of the performance obligations in the Company’s contracts with customers; • Assumptions used in the valuation of certain equity awards; and • Assumptions used in the calculation of goodwill impairment, including the forecast of future cash flows and discount rate. Actual results could differ from those estimates, and such differences could be material to the Company’s consolidated financial position and results of operations. Marketable Securities The Company's 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 non-current. The Company classifies its marketable securities as available-for-sale at the time of purchase based on its intent and are recorded at their estimated fair value. Unrealized gains for available-for-sale securities are recorded in other comprehensive income/loss. Unrealized losses for available-for-sale securities are recorded in other comprehensive income/loss, unless the losses relate to deterioration in credit risk or if it is likely securities will be sold before the recovery of their cost basis. In these cases, the unrealized losses are reported in other income, net in the consolidated statement of operations. Realized gains and losses are determined based on the specific identification method and are reported in other income, net in the consolidated statements of operations. Concentrations of Risk and Significant Customers The Company had one customer, Anthem Inc. ("Anthem"), that accounted for 49% and 46% of total revenue during the three and six months ended June 30, 2020, respectively, and 32% of accounts receivable as of June 30, 2020. Recently Adopted Accounting Pronouncements Effective January 1, 2020, the Company adopted Accounting Standards Update (“ASU”) 2016-13, Financial Instruments-Credit Losses, and subsequent amendments (“ASC 326”). The standard changes how entities will measure credit losses for most financial assets and certain other instruments that are not measured at fair value through net income. The adoption of this standard did not have a material impact on the Company’s financial statements. The Company will continue to actively monitor the impact of the current coronavirus (“COVID-19”) pandemic on expected credit losses. Effective January 1, 2020, the Company adopted ASU 2018-15, Intangibles – Goodwill and Other – Internal-Use Software (“ASU 2018-15”), which aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. The adoption of this standard did not have a material impact on the Company’s financial position or results of operations. Recently Issued Accounting Pronouncements The Company considers the applicability and impact of all ASUs issued by the FASB. The Company determined that the ASUs issued by the FASB during the six months ended June 30, 2020 are either not applicable or are expected to have minimal impact on the Company's condensed consolidated financial results.

Revenue, Deferred Revenue, Cont

Revenue, Deferred Revenue, Contract Balances and Performance Obligations	6 Months Ended
	Jun. 30, 2020
Revenue from Contract with Customer [Abstract]
Revenue, Deferred Revenue, Contract Balances and Performance Obligations	Revenue, Deferred Revenue, Contract Balances and Performance Obligations The Company sells to customers based in the United States. Starting January 1, 2020, the effective date of the Anthem enterprise license agreement, the Company began treating Anthem as a direct health plan customer rather than a channel partner. As a result, substantially all of the Company's revenues are generated through direct sales. Deferred revenue as of June 30, 2020 and December 31, 2019 was $13.5 million and $10.7 million, respectively. Contract assets as of June 30, 2020 and December 31, 2019 were $4.8 million and $0.4 million, respectively. The increase in contract assets is primarily due to the Anthem enterprise license agreement. Revenue of $6.6 million and $11.3 million was recognized during the three months ended June 30, 2020 and 2019, respectively, that was included in the Company’s deferred revenue balances at the beginning of the respective periods. Revenue of $8.8 million and $16.0 million was recognized during the six months ended June 30, 2020 and 2019, respectively, that was included in the Company’s deferred revenue balances at the beginning of the respective periods. The Company recorded favorable cumulative catch-up adjustments to revenue of $0.4 million and $0.5 million during the three months ended June 30, 2020 and 2019, respectively, arising from changes in estimates of transaction price. The Company recorded favorable cumulative catch-up adjustments to revenue of $2.1 million and $1.9 million during the six months ended June 30, 2020 and 2019, respectively, arising from changes in estimates of transaction price. The aggregate balance of remaining performance obligations from non-cancelable contracts with customers as of June 30, 2020 was $198.6 million. The Company expects to recognize approximately 60% of this balance over the next 12 months, with the remaining balance recognized thereafter. Remaining performance obligations are defined as deferred revenue and amounts yet to be billed for the non-cancelable portion of contracts.

Deferred Costs

Deferred Costs	6 Months Ended
	Jun. 30, 2020
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Deferred Costs	Deferred Costs Changes in the balance of total deferred commissions and total deferred professional service costs during the six months ended June 30, 2020 are as follows (in thousands): As of December 31, 2019 Expense recognized As of June 30, 2020 Additions Deferred commissions $ 14,718 $ 920 $ (3,919) $ 11,719 Deferred professional service costs 6,711 663 (1,657) 5,717 Total deferred commissions and professional service costs $ 21,429 $ 1,583 $ (5,576) $ 17,436 These costs are reviewed for impairment quarterly. Impairment charges were $0.2 million and $1.3 million for the three and six months ended June 30, 2020, respectively. Impairment charges for the three and six months ended June 30, 2019 were immaterial.

Goodwill and Intangible Assets

Goodwill and Intangible Assets	6 Months Ended
	Jun. 30, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	Goodwill and Intangible Assets Impairment The Company determined that the significant decline in the U.S. economy as a result of the COVID-19 pandemic, together with the decline in the Company’s stock price, constituted a triggering event, which required the Company to perform interim impairment analyses related to its long-lived assets and goodwill during the first quarter of 2020. The impairment analysis for long-lived assets indicated that the assets were recoverable; therefore, no impairment was recorded. After assessing long-lived assets, the Company performed a goodwill impairment analysis and determined that the carrying value of its only reporting unit exceeded its fair value by approximately $50.3 million. The fair value was determined using the income approach. The Company believes that the income approach is the most reliable indication of fair value since it incorporates future estimated revenues and expenses for the reporting unit that the market approach may not directly incorporate. In addition to future estimated revenue and expenses, the determination of fair value included assumptions related to a discount rate. During the second quarter of 2020, the Company determined that there were no indicators present to suggest that it was more likely than not that the fair value of the reporting unit was less than its carrying amount. The Company will continue to monitor its goodwill on a quarterly basis for indicators of impairment, including but not limited to, further declines in the stock price. Accordingly, there may be future impairments. Goodwill The Company’s goodwill relates entirely to the acquisition of Jiff in 2017. As of June 30, 2020, the gross amount of goodwill was $91.8 million and accumulated goodwill impairment was $50.3 million, all of which was recorded in the first quarter of 2020. The goodwill impairment did not involve any cash expenditures. Intangible assets, net Identified intangible assets are recorded at their estimated fair values at the date of acquisition and are amortized over their respective estimated useful lives using a method of amortization that reflects the pattern in which the economic benefits of the intangible assets are used. The following tables set forth the fair value components of identifiable acquired intangible assets (dollars in thousands): As of June 30, 2020 Useful Life Gross Accumulated Amortization Net Customer relationships 6 $ 10,900 $ (4,564) $ 6,336 Developed technology 5 10,600 (6,890) 3,710 Total identifiable intangible assets $ 21,500 $ (11,454) $ 10,046 As of December 31, 2019 Useful Life Gross Accumulated Amortization Net Customer relationships 6 $ 10,900 $ (3,509) $ 7,391 Developed technology 5 10,600 (5,830) 4,770 Backlog 2.5 1,500 (1,500) — Other acquired intangible assets 1 - 3 900 (883) 17 Total identifiable intangible assets $ 23,900 $ (11,722) $ 12,178 Amortization expense from acquired intangible assets for the three months ended June 30, 2020 and 2019 was $1.1 million and $0.9 million, respectively. Amortization expense from acquired intangible assets for the six months ended June 30, 2020 and 2019 was $2.1 million and $1.8 million, respectively. Amortization expense is included in cost of subscription, sales and marketing, and general and administrative expenses. Future estimated amortization expense for acquired intangible assets is as follows (in thousands): Remainder of 2020 $ 2,116 2021 4,232 2022 2,642 2023 1,056 Total amortization expense $ 10,046

Marketable Securities

Marketable Securities	6 Months Ended
	Jun. 30, 2020
Investments, Debt and Equity Securities [Abstract]
Marketable Securities	Marketable Securities Marketable securities consisted of the following (in thousands): As of June 30, 2020 Amortized Unrealized Unrealized Fair Value Money market mutual funds $ 2,759 $ — $ — $ 2,759 Included in cash and cash equivalents $ 2,759 $ — $ — $ 2,759 As of December 31, 2019 Amortized Unrealized Unrealized Fair Value U.S. treasury securities $ 13,602 $ 1 $ — $ 13,603 U.S. agency obligations 6,400 1 — 6,401 Money market mutual funds 8,736 — — 8,736 28,738 2 — 28,740 Included in cash and cash equivalents 12,329 — — 12,329 Included in marketable securities $ 16,409 $ 2 $ — $ 16,411

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 2020
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements The Company measures its financial assets and liabilities at fair value at each reporting period using a fair value hierarchy that requires that the Company 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. There were no significant transfers between fair value measurement levels as of June 30, 2020 and December 31, 2019. As of June 30, 2020 and December 31, 2019, there were no securities within Level 3 of the fair value hierarchy. The following tables present information about the Company’s assets and liabilities that are measured at fair value on a recurring basis using the above input categories (in thousands): As of June 30, 2020 Level 1 Level 2 Total Cash equivalents: Money market mutual funds $ 2,759 $ — $ 2,759 $ 2,759 $ — $ 2,759 As of December 31, 2019 Level 1 Level 2 Total Cash equivalents: Money market mutual funds $ 8,736 $ — $ 8,736 U.S. treasury securities — 3,593 3,593 Marketable securities: U.S. agency obligations — 6,401 6,401 U.S. treasury securities — 10,010 10,010 $ 8,736 $ 20,004 $ 28,740 Gross unrealized gains for cash equivalents and marketable securities as of June 30, 2020 and December 31, 2019 were not material.

Property and Equipment

Property and Equipment	6 Months Ended
	Jun. 30, 2020
Property, Plant and Equipment [Abstract]
Property and Equipment	Property and Equipment Property and equipment consisted of the following (in thousands): As of June 30, 2020 December 31, 2019 Leasehold improvements $ 4,663 $ 2,834 Computer equipment 8,224 8,126 Software 1,025 1,110 Internal-use software 3,878 2,925 Furniture and equipment 1,684 1,048 Construction in progress 128 1,164 Total 19,602 17,207 Less: accumulated depreciation (13,249) (12,351) Property and equipment, net $ 6,353 $ 4,856 Depreciation and amortization expense for the three months ended June 30, 2020 and 2019 was $0.6 million and $0.5 million, respectively. Depreciation and amortization expense for the six months ended June 30, 2020 and 2019 was $1.0 million and $0.9 million, respectively. Depreciation and amortization are recorded on a straight-line basis.

Debt

Debt	6 Months Ended
	Jun. 30, 2020
Debt Disclosure [Abstract]
Debt	Debt Term Loan The Company has a term loan facility (the “Loan Agreement”) with Silicon Valley Bank (the “Bank”) that provided for a term loan of approximately $5.6 million (the “Term Loan”). Obligations under the Term Loan accrue interest at a floating per annum rate equal to the greater of (A) the prime rate as published in the money rates section of The Wall Street Journal (“Prime Rate”) minus 1% or (B) 0%. Interest on the Term Loan is payable monthly. The maturity date of the Term Loan is September 1, 2021. In addition to principal and interest payments, the Company is also required to pay $0.5 million as final payment on the earlier of maturity, termination or prepayment of the Term Loan. The Company accrues for the final payment over the life of the Term Loan using the effective interest method. The future maturities of the Term Loan by year as of June 30, 2020 are as follows (in thousands): Remainder of 2020 $ 929 2021 (1) 1,395 Total future maturities of debt 2,324 Less current maturities (2) (1,859) Debt, non-current $ 465 (1) Excludes the $0.5 million required to be paid as final payment on the earlier of maturity, termination or prepayment of the Term Loan. (2) Classified within accrued expenses and other current liabilities on the condensed consolidated balance sheet as of June 30, 2020. Per the Loan Agreement the Company is subject to certain reporting covenants, and the debt obligations are secured by a security interest in the assets of the Company, excluding intellectual property and certain other exceptions. The Company was in compliance with all reporting covenants in the Loan Agreement related to the outstanding principal balance as of June 30, 2020. Revolving Line of Credit On May 5, 2020, the Company entered into the Third Amended and Restated Loan and Security Agreement (the "Amended Loan Agreement") with the Bank. The Amended Loan Agreement amended and restated its existing Loan Agreement. Under the Amended Loan Agreement, the Bank agreed to extend a $25.0 million revolving credit facility to the Company (the “Revolving Line”). Borrowings under the Revolving Line accrue interest at a floating per annum rate equal to the Prime Rate plus 1%, and such interest is payable monthly. The Company may request borrowings under the Revolving Line prior to May 4, 2023, on which date the Revolving Line terminates. In relation to the Revolving Line, the Company is subject to certain financial and reporting covenants. As of June 30, 2020, no borrowings have been made under the Revolving Line, and the Company was in compliance with all financial and reporting covenants. Paycheck Protection Program Loan On April 22, 2020, the Company entered into a Paycheck Protection Program Loan (the “PPP Note”) sponsored by the Small Business Administration (the “SBA”) through the Bank, providing for $10.0 million in proceeds. The PPP Note was issued pursuant to the Paycheck Protection Program under the Coronavirus Aid, Relief, and Economic Security Act (the “CARES Act”). The PPP Note was scheduled to mature on April 22, 2022, carried an interest rate of 1% per annum, and was subject to the terms and conditions applicable to all loans made pursuant to the Paycheck Protection Program as administered by the SBA under the CARES Act, including the debt forgiveness provisions contained therein. Following additional guidance issued by the SBA on April 23, 2020 that cast doubt on the ability of public companies to qualify for loans under the Paycheck Protection Program, the Company repaid the PPP Note on April 29, 2020.

Contingencies

Contingencies	6 Months Ended
	Jun. 30, 2020
Commitments and Contingencies Disclosure [Abstract]
Contingencies	Contingencies Legal Matters From time to time, the Company may become subject to legal proceedings, claims or litigation arising in the ordinary course of business. In addition, the Company may receive letters alleging infringement of patents or other intellectual property rights. If an unfavorable outcome were to occur in litigation, the impact could be material to the Company’s business, financial condition, cash flow or results of operations, depending on the specific circumstances of the outcome. The Company accrues for loss contingencies when it is both probable that it will incur the loss and when it can reasonably estimate the amount of the loss or range of loss.

Stock Compensation

Stock Compensation	6 Months Ended
	Jun. 30, 2020
Share-based Payment Arrangement [Abstract]
Stock Compensation	Stock Compensation Restricted Stock Units (“RSUs”) Activity A summary of unvested restricted stock unit activity for the six months ended June 30, 2020 is as follows: Number of Weighted- Balance as of December 31, 2019 11,615,884 $ 2.44 Granted 12,299,276 $ 0.88 Vested (2,032,476) $ 2.77 Forfeited and canceled (3,268,027) $ 2.51 Balance as of June 30, 2020 18,614,657 $ 1.36 As of June 30, 2020, there was a total of $22.5 million in unrecognized compensation cost related to restricted stock units, which is expected to be recognized over a weighted-average period of approximately 2.7 years. The Company granted approximately 0.9 million performance stock units ("PSUs") during the third quarter of 2019. The number of shares that will eventually vest depends on achievement of certain performance targets, as determined by the compensation committee of the Company's board of directors. Once the performance is determined, the PSUs, if any, will vest, subject to recipients' continued service, on the later of (i) the attainment of the performance targets and (ii) a year after the grant date. The compensation expense associated with the PSUs is recognized using the accelerated method. For the three and six months ended June 30, 2020, the Company recognized compensation expense of approximately $0.6 million and $0.8 million, respectively, related to these performance awards. Stock Option Activity A summary of stock option activity for the six months ended June 30, 2020 is as follows: Options Weighted- Aggregate Balance as of December 31, 2019 7,207,733 $ 1.94 $ 412 Granted 749,111 $ 1.17 Exercised (142,729) $ 1.08 Forfeited and canceled (2,117,240) $ 1.71 Balance as of June 30, 2020 5,696,875 $ 1.94 $ 2 The total grant-date fair value of stock options granted during the six months ended June 30, 2020 and 2019 was $0.6 million and $0.4 million, respectively. 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: Six Months Ended June 30, 2020 2019 Volatility 73% 57% Expected life (in years) 6.11 - 6.12 6.06 Risk-free interest rate 0.84% - 1.47% 2.57% Dividend yield —% —% As of June 30, 2020, the Company had $2.6 million in unrecognized compensation cost related to non-vested stock options, which is expected to be recognized over a weighted-average period of approximately 3.2 years. Employee Stock Purchase Plan The Company used the following Black-Scholes assumptions in estimating the fair value of the shares under the 2014 Employee Stock Purchase Plan (the “ESPP”): Six Months Ended June 30, 2020 Volatility 71% Expected life equals length of offering period (in years) 0.5 Risk-free interest rate 0.95% Dividend yield —% Stock-based compensation expense related to the ESPP was immaterial for the three and six months ended June 30, 2020. As of June 30, 2020, the unrecognized stock-based compensation expense related to the ESPP was also immaterial, and is expected to be recognized over the remaining term of the offering period.

Income Taxes

Income Taxes	6 Months Ended
	Jun. 30, 2020
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The effective tax rate for the three and six months ended June 30, 2020 and 2019 was zero percent, primarily as a result of the estimated tax loss for the year and the change in valuation allowance. At June 30, 2020, all unrecognized tax benefits are subject to a full valuation allowance and, if recognized, will not affect the effective tax rate.

Net Loss per Share

Net Loss per Share	6 Months Ended
	Jun. 30, 2020
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. Diluted net loss per share is computed by giving effect to all potential shares of common stock, including 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. 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. The following table presents the calculation of basic and diluted net loss per share for the Company’s common stock (in thousands, except per share data): Three Months Ended June 30, Six Months Ended June 30, 2020 2019 2020 2019 Class A Class B Class A Class B Class A Class B Class A Class B Net loss $ (981) $ (3,223) $ (2,026) $ (6,355) $ (14,188) $ (46,351) $ (4,767) $ (14,153) Weighted-average shares used to compute basic and diluted net loss per share 35,030 115,048 35,276 109,296 35,031 114,444 36,227 107,563 Basic and diluted net loss per share $ (0.03) $ (0.03) $ (0.06) $ (0.06) $ (0.41) $ (0.41) $ (0.13) $ (0.13) 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): Three Months Ended June 30, Six Months Ended June 30, 2020 2019 2020 2019 Stock options and restricted stock units 24,312 16,157 24,312 16,157 Shares issuable under the ESPP 297 — 297 — Warrants 115 115 115 115 Total 24,724 16,272 24,724 16,272

Restructuring Program

Restructuring Program	6 Months Ended
	Jun. 30, 2020
Restructuring and Related Activities [Abstract]
Restructuring Program	Restructuring Program On May 4, 2020, the Company announced its intent to undertake a program to reduce its workforce as part of the Company’s efforts to respond to the COVID-19 pandemic and ensure longer-term financial stability for the Company in light of the ongoing economic challenges resulting from COVID-19 and its impact on the Company’s business (the “Program”). The Program involves the termination of approximately 60 employees, representing 13% of the Company’s headcount. For the three months ended June 30, 2020, the Company incurred charges of approximately $2.0 million related to employee severance and benefits costs under the Program, all of which are cash expenditures. As of June 30, 2020, $1.6 million of the total has been paid out, and the remaining balance of $0.4 million is expected to be paid by September 30, 2020.In addition, as part of its cost reductions in light of the COVID-19 pandemic, the Company has implemented reductions in base salary for its employees, effective May 16, 2020, consisting of a 30% reduction for the Company’s Chief Executive Officer, 25% reduction for the Company’s Chief Financial Officer, 20% reduction for members of the Company’s executive leadership team, and tiered reductions of 10-15% for other employees with salaries above $100,000, which the Company anticipates will last at least six months, and will be re-evaluated at that time. Members of the Company’s Board of Directors have also voluntarily agreed to forego 50% of their cash compensation for the duration of the employee salary reductions.

Accounting Standards and Sign_2

Accounting Standards and Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2020
Accounting Policies [Abstract]
Basis of Presentation and Principles of Consolidation	Basis of Presentation and Principles of Consolidation The accompanying unaudited condensed consolidated financial statements include Castlight and its wholly-owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) and applicable rules and regulations of the Securities and Exchange Commission (“SEC”) regarding interim financial reporting. 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, stockholders’ equity and cash flows. The results for the interim periods presented are not necessarily indicative of the results expected for any future period. The following information should be read in conjunction with the audited financial statements and notes thereto included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019. Other than as described below, there have been no changes to the Company's significant accounting policies described in the Company's Annual Report that have had a material impact on the Company's consolidated financial statements and related notes.
Use of Estimates	Use of Estimates The preparation of condensed consolidated financial statements in conformity with GAAP requires the Company 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: • Variable consideration included in the transaction price of the Company’s contracts with customers; • The standalone selling price of the performance obligations in the Company’s contracts with customers; • Assumptions used in the valuation of certain equity awards; and • Assumptions used in the calculation of goodwill impairment, including the forecast of future cash flows and discount rate. Actual results could differ from those estimates, and such differences could be material to the Company’s consolidated financial position and results of operations.
Marketable Securities	Marketable Securities The Company's 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 non-current. The Company classifies its marketable securities as available-for-sale at the time of purchase based on its intent and are recorded at their estimated fair value. Unrealized gains for available-for-sale securities are recorded in other comprehensive income/loss. Unrealized losses for available-for-sale securities are recorded in other comprehensive income/loss, unless the losses relate to deterioration in credit risk or if it is likely securities will be sold before the recovery of their cost basis. In these cases, the unrealized losses are reported in other income, net in the consolidated statement of operations.
Recently Adopted Accounting Pronouncements and Recently Issued Accounting Pronouncements	Recently Adopted Accounting Pronouncements Effective January 1, 2020, the Company adopted Accounting Standards Update (“ASU”) 2016-13, Financial Instruments-Credit Losses, and subsequent amendments (“ASC 326”). The standard changes how entities will measure credit losses for most financial assets and certain other instruments that are not measured at fair value through net income. The adoption of this standard did not have a material impact on the Company’s financial statements. The Company will continue to actively monitor the impact of the current coronavirus (“COVID-19”) pandemic on expected credit losses. Effective January 1, 2020, the Company adopted ASU 2018-15, Intangibles – Goodwill and Other – Internal-Use Software (“ASU 2018-15”), which aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. The adoption of this standard did not have a material impact on the Company’s financial position or results of operations. Recently Issued Accounting Pronouncements The Company considers the applicability and impact of all ASUs issued by the FASB. The Company determined that the ASUs issued by the FASB during the six months ended June 30, 2020 are either not applicable or are expected to have minimal impact on the Company's condensed consolidated financial results.

Deferred Costs (Tables)

Deferred Costs (Tables)	6 Months Ended
	Jun. 30, 2020
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Changes in Balance of Total Deferred Commissions and Total Deferred Professional Service Costs	Changes in the balance of total deferred commissions and total deferred professional service costs during the six months ended June 30, 2020 are as follows (in thousands): As of December 31, 2019 Expense recognized As of June 30, 2020 Additions Deferred commissions $ 14,718 $ 920 $ (3,919) $ 11,719 Deferred professional service costs 6,711 663 (1,657) 5,717 Total deferred commissions and professional service costs $ 21,429 $ 1,583 $ (5,576) $ 17,436

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	6 Months Ended
	Jun. 30, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Finite-Lived Intangible Assets	The following tables set forth the fair value components of identifiable acquired intangible assets (dollars in thousands): As of June 30, 2020 Useful Life Gross Accumulated Amortization Net Customer relationships 6 $ 10,900 $ (4,564) $ 6,336 Developed technology 5 10,600 (6,890) 3,710 Total identifiable intangible assets $ 21,500 $ (11,454) $ 10,046 As of December 31, 2019 Useful Life Gross Accumulated Amortization Net Customer relationships 6 $ 10,900 $ (3,509) $ 7,391 Developed technology 5 10,600 (5,830) 4,770 Backlog 2.5 1,500 (1,500) — Other acquired intangible assets 1 - 3 900 (883) 17 Total identifiable intangible assets $ 23,900 $ (11,722) $ 12,178
Schedule of Amortization Expense for Acquired Intangible Assets	Future estimated amortization expense for acquired intangible assets is as follows (in thousands): Remainder of 2020 $ 2,116 2021 4,232 2022 2,642 2023 1,056 Total amortization expense $ 10,046

Marketable Securities (Tables)

Marketable Securities (Tables)	6 Months Ended
	Jun. 30, 2020
Investments, Debt and Equity Securities [Abstract]
Available-for-sale Securities	Marketable securities consisted of the following (in thousands): As of June 30, 2020 Amortized Unrealized Unrealized Fair Value Money market mutual funds $ 2,759 $ — $ — $ 2,759 Included in cash and cash equivalents $ 2,759 $ — $ — $ 2,759 As of December 31, 2019 Amortized Unrealized Unrealized Fair Value U.S. treasury securities $ 13,602 $ 1 $ — $ 13,603 U.S. agency obligations 6,400 1 — 6,401 Money market mutual funds 8,736 — — 8,736 28,738 2 — 28,740 Included in cash and cash equivalents 12,329 — — 12,329 Included in marketable securities $ 16,409 $ 2 $ — $ 16,411

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2020
Fair Value Disclosures [Abstract]
Fair Value, Assets Measured on Recurring Basis	The following tables present information about the Company’s assets and liabilities that are measured at fair value on a recurring basis using the above input categories (in thousands): As of June 30, 2020 Level 1 Level 2 Total Cash equivalents: Money market mutual funds $ 2,759 $ — $ 2,759 $ 2,759 $ — $ 2,759 As of December 31, 2019 Level 1 Level 2 Total Cash equivalents: Money market mutual funds $ 8,736 $ — $ 8,736 U.S. treasury securities — 3,593 3,593 Marketable securities: U.S. agency obligations — 6,401 6,401 U.S. treasury securities — 10,010 10,010 $ 8,736 $ 20,004 $ 28,740

Property and Equipment (Tables)

Property and Equipment (Tables)	6 Months Ended
	Jun. 30, 2020
Property, Plant and Equipment [Abstract]
Property and Equipment	Property and equipment consisted of the following (in thousands): As of June 30, 2020 December 31, 2019 Leasehold improvements $ 4,663 $ 2,834 Computer equipment 8,224 8,126 Software 1,025 1,110 Internal-use software 3,878 2,925 Furniture and equipment 1,684 1,048 Construction in progress 128 1,164 Total 19,602 17,207 Less: accumulated depreciation (13,249) (12,351) Property and equipment, net $ 6,353 $ 4,856

Debt (Tables)

Debt (Tables)	6 Months Ended
	Jun. 30, 2020
Debt Disclosure [Abstract]
Schedule of Maturities of Long-term Debt	The future maturities of the Term Loan by year as of June 30, 2020 are as follows (in thousands): Remainder of 2020 $ 929 2021 (1) 1,395 Total future maturities of debt 2,324 Less current maturities (2) (1,859) Debt, non-current $ 465 (1) Excludes the $0.5 million required to be paid as final payment on the earlier of maturity, termination or prepayment of the Term Loan. (2) Classified within accrued expenses and other current liabilities on the condensed consolidated balance sheet as of June 30, 2020.

Stock Compensation (Tables)

Stock Compensation (Tables)	6 Months Ended
	Jun. 30, 2020
Share-based Payment Arrangement [Abstract]
Schedule of Other Share-based Compensation, Activity	A summary of unvested restricted stock unit activity for the six months ended June 30, 2020 is as follows: Number of Weighted- Balance as of December 31, 2019 11,615,884 $ 2.44 Granted 12,299,276 $ 0.88 Vested (2,032,476) $ 2.77 Forfeited and canceled (3,268,027) $ 2.51 Balance as of June 30, 2020 18,614,657 $ 1.36
Schedule of Share-based Compensation, Stock Options, Activity	A summary of stock option activity for the six months ended June 30, 2020 is as follows: Options Weighted- Aggregate Balance as of December 31, 2019 7,207,733 $ 1.94 $ 412 Granted 749,111 $ 1.17 Exercised (142,729) $ 1.08 Forfeited and canceled (2,117,240) $ 1.71 Balance as of June 30, 2020 5,696,875 $ 1.94 $ 2
Schedule of Share-based Payment Award, 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: Six Months Ended June 30, 2020 2019 Volatility 73% 57% Expected life (in years) 6.11 - 6.12 6.06 Risk-free interest rate 0.84% - 1.47% 2.57% Dividend yield —% —% The Company used the following Black-Scholes assumptions in estimating the fair value of the shares under the 2014 Employee Stock Purchase Plan (the “ESPP”): Six Months Ended June 30, 2020 Volatility 71% Expected life equals length of offering period (in years) 0.5 Risk-free interest rate 0.95% Dividend yield —%

Net Loss per Share (Tables)

Net Loss per Share (Tables)	6 Months Ended
	Jun. 30, 2020
Earnings Per Share [Abstract]
Calculation of Basic and Diluted Earnings per Share	The following table presents the calculation of basic and diluted net loss per share for the Company’s common stock (in thousands, except per share data): Three Months Ended June 30, Six Months Ended June 30, 2020 2019 2020 2019 Class A Class B Class A Class B Class A Class B Class A Class B Net loss $ (981) $ (3,223) $ (2,026) $ (6,355) $ (14,188) $ (46,351) $ (4,767) $ (14,153) Weighted-average shares used to compute basic and diluted net loss per share 35,030 115,048 35,276 109,296 35,031 114,444 36,227 107,563 Basic and diluted net loss per share $ (0.03) $ (0.03) $ (0.06) $ (0.06) $ (0.41) $ (0.41) $ (0.13) $ (0.13)
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): Three Months Ended June 30, Six Months Ended June 30, 2020 2019 2020 2019 Stock options and restricted stock units 24,312 16,157 24,312 16,157 Shares issuable under the ESPP 297 — 297 — Warrants 115 115 115 115 Total 24,724 16,272 24,724 16,272

Accounting Standards and Sign_3

Accounting Standards and Significant Accounting Policies - Concentrations of Risk and Significant Customers (Details) - Customer Concentration Risk - Anthem	3 Months Ended	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2020
Total Revenue
Concentration Risk [Line Items]
Concentration risk, percentage	49.00%	46.00%
Accounts Receivable
Concentration Risk [Line Items]
Concentration risk, percentage		32.00%

Revenue, Deferred Revenue, Co_2

Revenue, Deferred Revenue, Contract Balances and Performance Obligations - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Revenue from Contract with Customer [Abstract]
Deferred revenue	$ 13.5		$ 13.5		$ 10.7
Contract with customer, asset, net	4.8		4.8		$ 0.4
Contract with customer liability, revenue recognized	6.6	$ 11.3	8.8	$ 16
Contract with customer, liability, cumulative catch-up adjustment to revenue, change in estimate of transaction price	$ 0.4	$ 0.5	$ 2.1	$ 1.9

Revenue, Deferred Revenue, Co_3

Revenue, Deferred Revenue, Contract Balances and Performance Obligations - Performance Obligations (Details) $ in Millions	Jun. 30, 2020USD ($)
Revenue from Contract with Customer [Abstract]
Revenue, remaining performance obligation	$ 198.6
Revenue, remaining performance obligation, percent	60.00%
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-04-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation, expected timing of satisfaction, period	12 months

Deferred Costs (Details)

Deferred Costs (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2020
Deferred commissions
As of beginning of period		$ 14,718
Additions		920
Expense recognized		(3,919)
As of end of period	$ 11,719	11,719
Deferred professional service costs
As of beginning of period		6,711
Additions		663
Expense recognized		(1,657)
As of end of period	5,717	5,717
Total deferred commissions and professional service costs
As of beginning of period		21,429
Additions		1,583
Expense recognized		(5,576)
As of end of period	17,436	17,436
Impairment charges	$ 200	$ 1,300

Goodwill and Intangible Asset_2

Goodwill and Intangible Assets - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill impairment	$ 0	$ 0	$ 50,300	$ 0
Gross goodwill	91,800		91,800
Accumulated goodwill impairment	50,300		50,300
Amortization expense	$ 1,100	$ 900	$ 2,100	$ 1,800

Goodwill and Intangible Asset_3

Goodwill and Intangible Assets - Schedule of Finite-Lived Intangible Assets (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Finite-lived Intangible Assets [Roll Forward]
Gross	$ 21,500	$ 23,900
Accumulated Amortization	(11,454)	(11,722)
Total	$ 10,046	$ 12,178
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Useful Life	6 years	6 years
Finite-lived Intangible Assets [Roll Forward]
Gross	$ 10,900	$ 10,900
Accumulated Amortization	(4,564)	(3,509)
Total	$ 6,336	$ 7,391
Developed technology
Finite-Lived Intangible Assets [Line Items]
Useful Life	5 years	5 years
Finite-lived Intangible Assets [Roll Forward]
Gross	$ 10,600	$ 10,600
Accumulated Amortization	(6,890)	(5,830)
Total	$ 3,710	$ 4,770
Backlog
Finite-Lived Intangible Assets [Line Items]
Useful Life		2 years 6 months
Finite-lived Intangible Assets [Roll Forward]
Gross		$ 1,500
Accumulated Amortization		(1,500)
Total		0
Other acquired intangible assets
Finite-lived Intangible Assets [Roll Forward]
Gross		900
Accumulated Amortization		(883)
Total		$ 17
Other acquired intangible assets | Minimum
Finite-Lived Intangible Assets [Line Items]
Useful Life		1 year
Other acquired intangible assets | Maximum
Finite-Lived Intangible Assets [Line Items]
Useful Life		3 years

Goodwill and Intangible Asset_4

Goodwill and Intangible Assets - Schedule of Amortization Expense for Acquired Intangible Assets (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Remainder of 2020	$ 2,116
2021	4,232
2022	2,642
2023	1,056
Total	$ 10,046	$ 12,178

Marketable Securities (Details)

Marketable Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Amortized Cost		$ 28,738
Unrealized Gains		2
Unrealized Losses		0
Fair Value		28,740
Included in cash and cash equivalents
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 2,759	12,329
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	2,759	12,329
Included in marketable securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost		16,409
Unrealized Gains		2
Unrealized Losses		0
Fair Value		16,411
U.S. treasury securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost		13,602
Unrealized Gains		1
Unrealized Losses		0
Fair Value		13,603
U.S. agency obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost		6,400
Unrealized Gains		1
Unrealized Losses		0
Fair Value		6,401
Money market mutual funds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2,759	8,736
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair Value	$ 2,759	$ 8,736

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Assets Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities		$ 28,740
Money market mutual funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	$ 2,759	8,736
U.S. treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities		13,603
U.S. agency obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities		6,401
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value disclosure	2,759	28,740
Fair Value, Measurements, Recurring | Money market mutual funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	2,759	8,736
Fair Value, Measurements, Recurring | U.S. treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents		3,593
Marketable securities		10,010
Fair Value, Measurements, Recurring | U.S. agency obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities		6,401
Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value disclosure	2,759	8,736
Fair Value, Measurements, Recurring | Level 1 | Money market mutual funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	2,759	8,736
Fair Value, Measurements, Recurring | Level 1 | U.S. treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents		0
Marketable securities		0
Fair Value, Measurements, Recurring | Level 1 | U.S. agency obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities		0
Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value disclosure	0	20,004
Fair Value, Measurements, Recurring | Level 2 | Money market mutual funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	$ 0	0
Fair Value, Measurements, Recurring | Level 2 | U.S. treasury securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents		3,593
Marketable securities		10,010
Fair Value, Measurements, Recurring | Level 2 | U.S. agency obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities		$ 6,401

Property and Equipment - Schedu

Property and Equipment - Schedule of Property, Plant and Equipment (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Property and equipment	$ 19,602	$ 17,207
Less: accumulated depreciation	(13,249)	(12,351)
Property and equipment, net	6,353	4,856
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment	4,663	2,834
Computer equipment
Property, Plant and Equipment [Line Items]
Property and equipment	8,224	8,126
Software
Property, Plant and Equipment [Line Items]
Property and equipment	1,025	1,110
Internal-use software
Property, Plant and Equipment [Line Items]
Property and equipment	3,878	2,925
Furniture and equipment
Property, Plant and Equipment [Line Items]
Property and equipment	1,684	1,048
Construction in progress
Property, Plant and Equipment [Line Items]
Property and equipment	$ 128	$ 1,164

Property and Equipment - Narrat

Property and Equipment - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Property, Plant and Equipment [Abstract]
Depreciation expense	$ 0.6	$ 0.5	$ 1	$ 0.9

Debt - Narrative (Details)

Debt - Narrative (Details) - USD ($)	May 05, 2020	Jun. 30, 2020	Apr. 22, 2020
Line of Credit Facility [Line Items]
Term Loan		$ 5,600,000
Early repayment of senior debt		500,000
PPP Note
Line of Credit Facility [Line Items]
Term Loan			$ 10,000,000
Debt instrument, interest rate, stated percentage			1.00%
Line of Credit | Revolving credit
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity	$ 25,000,000
Borrowings		$ 0
Interest Rate Option A
Line of Credit Facility [Line Items]
Spread on variable rate		(1.00%)
Interest Rate Option B
Line of Credit Facility [Line Items]
Debt instrument, interest rate, stated percentage		0.00%
Prime rate | Line of Credit | Revolving credit
Line of Credit Facility [Line Items]
Spread on variable rate	1.00%

Debt - Future Maturities (Detai

Debt - Future Maturities (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Debt Disclosure [Abstract]
Remainder of 2020	$ 929
2021	1,395
Total future maturities of debt	2,324
Less current maturities	(1,859)
Debt, non-current	465	$ 1,395
Early repayment of senior debt	$ 500

Stock Compensation - Summary of

Stock Compensation - Summary of Restricted Stock Unit Activity (Details) - RSUs	6 Months Ended
	Jun. 30, 2020$ / sharesshares
Number of Shares
Balance as of beginning of period (in shares) | shares	11,615,884
Granted (in shares) | shares	12,299,276
Vested (in shares) | shares	(2,032,476)
Forfeited and canceled (in shares) | shares	(3,268,027)
Balance as of end of period (in shares) | shares	18,614,657
Weighted- Average Grant Date Fair Value
Balance as of beginning of period (in usd per share) | $ / shares	$ 2.44
Granted (in usd per share) | $ / shares	0.88
Vested (in usd per share) | $ / shares	2.77
Forfeited and canceled (in usd per share) | $ / shares	2.51
Balance as of end of period (in usd per share) | $ / shares	$ 1.36

Stock Compensation - Narrative

Stock Compensation - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Sep. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost	$ 22.5		$ 22.5
Employee service share-based compensation, nonvested awards, compensation cost not yet recognized, period for recognition			2 years 8 months 12 days
Granted (in shares)			12,299,276
PSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)		900,000
Stock-based compensation expense	0.6		$ 0.8
Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee service share-based compensation, nonvested awards, compensation cost not yet recognized, period for recognition			3 years 2 months 12 days
Stock granted, value, share-based compensation, gross			$ 0.6	$ 0.4
Employee service share-based compensation, nonvested awards, compensation not yet recognized, stock options	$ 2.6		$ 2.6

Stock Compensation - Summary _2

Stock Compensation - Summary of Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Options Outstanding
Balance as of beginning of period (in shares)	7,207,733
Granted (in shares)	749,111
Exercised (in shares)	(142,729)
Forfeited and canceled (in shares)	(2,117,240)
Balance as of end of period (in shares)	5,696,875
Weighted- Average Exercise Price
Balance as of beginning of period (in usd per share)	$ 1.94
Granted (in usd per share)	1.17
Exercised (in usd per share)	1.08
Forfeited and canceled (in usd per share)	1.71
Balance as of end of period (in usd per share)	$ 1.94
Aggregate Intrinsic Value (in thousands)
Aggregate Intrinsic Value	$ 2	$ 412

Stock Compensation - Assumption

Stock Compensation - Assumptions Related to Share-based Compensation (Details)	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Volatility	73.00%	57.00%
Expected life (in years)		6 years 21 days
Risk-free interest rate		2.57%
Dividend yield	0.00%	0.00%
Stock Option | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life (in years)	6 years 1 month 9 days
Risk-free interest rate	0.84%
Stock Option | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life (in years)	6 years 1 month 13 days
Risk-free interest rate	1.47%
ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Volatility	71.00%
Expected life (in years)	6 months
Risk-free interest rate	0.95%
Dividend yield	0.00%

Income Taxes (Details)

Income Taxes (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Income Tax Disclosure [Abstract]
Effective income tax rate reconciliation, percent	0.00%	0.00%	0.00%	0.00%

Net Loss per Share - Calculatio

Net Loss per Share - Calculation of Basic and Diluted Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Class of Stock [Line Items]
Net loss	$ (4,204)	$ (8,381)	$ (60,539)	$ (18,920)
Weighted-average shares used to compute basic and diluted net loss per share (in shares)	150,078	144,572	149,475	143,790
Basic and diluted net loss per share (in usd per share)	$ (0.03)	$ (0.06)	$ (0.41)	$ (0.13)
Class A
Class of Stock [Line Items]
Net loss	$ (981)	$ (2,026)	$ (14,188)	$ (4,767)
Weighted-average shares used to compute basic and diluted net loss per share (in shares)	35,030	35,276	35,031	36,227
Basic and diluted net loss per share (in usd per share)	$ (0.03)	$ (0.06)	$ (0.41)	$ (0.13)
Class B
Class of Stock [Line Items]
Net loss	$ (3,223)	$ (6,355)	$ (46,351)	$ (14,153)
Weighted-average shares used to compute basic and diluted net loss per share (in shares)	115,048	109,296	114,444	107,563
Basic and diluted net loss per share (in usd per share)	$ (0.03)	$ (0.06)	$ (0.41)	$ (0.13)

Net Loss per Share - Summary of

Net Loss per Share - Summary of Antidilutive Securities (Details) - shares shares in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securities excluded from the calculation of diluted net loss per share (in shares)	24,724	16,272	24,724	16,272
Stock options and restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securities excluded from the calculation of diluted net loss per share (in shares)	24,312	16,157	24,312	16,157
Shares issuable under the ESPP
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securities excluded from the calculation of diluted net loss per share (in shares)	297	0	297	0
Warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securities excluded from the calculation of diluted net loss per share (in shares)	115	115	115	115

Restructuring Program (Details)

Restructuring Program (Details) $ in Millions	May 16, 2020	May 04, 2020employee	Jun. 30, 2020USD ($)
Chief Executive Officer
Restructuring Cost and Reserve [Line Items]
Salary reduction percent	30.00%
Chief Financial Officer
Restructuring Cost and Reserve [Line Items]
Salary reduction percent	25.00%
Executive leadership team
Restructuring Cost and Reserve [Line Items]
Salary reduction percent	20.00%
Other employees with salaries above $100,000 | Minimum
Restructuring Cost and Reserve [Line Items]
Salary reduction percent	10.00%
Other employees with salaries above $100,000 | Maximum
Restructuring Cost and Reserve [Line Items]
Salary reduction percent	15.00%
Board of directors
Restructuring Cost and Reserve [Line Items]
Salary reduction percent	50.00%
The Program
Restructuring Cost and Reserve [Line Items]
Terminated employees | employee		60
Reduction in workforce, percent		13.00%
Employee severance and benefits costs			$ 2
Restructuring charges paid			1.6
Remaining balance			$ 0.4

Uncategorized Items - cslt-2020

Label	Element	Value
Restricted Cash, Current	us-gaap_RestrictedCashCurrent	$ 181,000
Restricted Cash, Current	us-gaap_RestrictedCashCurrent	$ 0