Document and Entity Information - shares	3 Months Ended
Document and Entity Information - shares	Mar. 31, 2019	Apr. 26, 2019
Document And Entity Information [Abstract]
Entity Registrant Name	CHEGG, INC
Entity Central Index Key	0001364954
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	Mar. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q1
Amendment Flag	false
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Common Stock, Shares Outstanding		118,548,013

CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Current assets
Cash and cash equivalents	$ 914,500	$ 374,664
Short-term investments	70,080	93,345
Accounts receivable, net of allowance for doubtful accounts of $27 and $229 at March 31, 2019 and December 31, 2018, respectively	8,870	12,733
Prepaid expenses	15,739	4,673
Other current assets	9,691	9,510
Total current assets	1,018,880	494,925
Long-term investments	12,533	16,052
Property and equipment, net	72,937	59,904
Goodwill	149,481	149,524
Intangible assets, net	24,097	25,915
Right of use assets	15,875	0
Other assets	15,412	14,618
Total assets	1,309,215	760,938
Current liabilities
Accounts payable	6,341	8,177
Deferred revenue	26,276	17,418
Current operating lease liabilities	4,640	0
Accrued liabilities	35,706	34,077
Total current liabilities	72,963	59,672
Long-term liabilities
Convertible senior notes, net	789,380	283,668
Long-term operating lease liabilities	15,424	0
Other long-term liabilities	3,311	6,964
Total long-term liabilities	808,115	290,632
Total liabilities	881,078	350,304
Commitments and contingencies (Note 9)
Stockholders' equity:
Preferred stock, $0.001 par value – 10,000,000 shares authorized, no shares issued and outstanding	0	0
Common stock, $0.001 par value 400,000,000 shares authorized; 118,196,707 and 115,500,418 shares issued and outstanding at March 31, 2019 and December 31, 2018, respectively	118	116
Additional paid-in capital	839,924	818,113
Accumulated other comprehensive loss	(900)	(1,019)
Accumulated deficit	(411,005)	(406,576)
Total stockholders' equity	428,137	410,634
Total liabilities and stockholders' equity	$ 1,309,215	$ 760,938

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Allowance for doubtful accounts receivable, current	$ 27	$ 229
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized	400,000,000	400,000,000
Common stock, shares issued	118,196,707	115,500,418
Common stock, shares outstanding	118,196,707	115,500,418

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Income Statement [Abstract]
Net revenues	$ 97,409	$ 76,949
Cost of revenues	23,335	20,224
Gross profit	74,074	56,725
Operating expenses:
Research and development	32,692	25,533
Sales and marketing	18,717	15,336
General and administrative	23,670	18,256
Restructuring charges	22	220
Total operating expenses	75,101	59,345
Loss from operations	(1,027)	(2,620)
Interest expense and other income, net:
Interest expense, net	(4,232)	(20)
Other income, net	1,567	564
Total interest expense and other income, net	(2,665)	544
Loss before provision for income taxes	(3,692)	(2,076)
Provision for income taxes	626	541
Net loss	$ (4,318)	$ (2,617)
Net loss per share, basic and diluted (in dollars per share)	$ (0.04)	$ (0.02)
Weighted average shares used to compute net loss per share, basic and diluted (in shares)	116,730	110,904

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Statement of Comprehensive Income [Abstract]
Net loss	$ (4,318)	$ (2,617)
Other comprehensive income:
Change in net unrealized gain (loss) on available for sale investments, net of tax	119	(91)
Change in foreign currency translation adjustments, net of tax	0	511
Other comprehensive income	119	420
Total comprehensive loss	$ (4,199)	$ (2,197)

- Definition

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

+ References + Details

CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Unaudited) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit
Common stock, beginning balance (in shares) at Dec. 31, 2017		109,668,000
Beginning balance at Dec. 31, 2017	$ 391,062	$ 110	$ 782,845	$ (282)	$ (391,611)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options and ESPP (in shares)		628,000
Issuance of common stock upon exercise of stock options and ESPP	5,219	$ 1	5,218
Net issuance of common stock for settlement of RSUs (in shares)		2,419,000
Net issuance of common stock for settlement of RSUs	(35,638)	$ 2	(35,640)
Warrant exercises (in shares)		34,000
Warrant exercises	0		0
Share-based compensation expense	11,642		11,642
Other comprehensive income	420			420
Net loss	(2,617)				(2,617)
Beginning balance at Mar. 31, 2018	$ 370,011	$ 113	764,065	138	(394,305)
Common stock, ending balance (in shares) at Mar. 31, 2018		112,749,000
Common stock, beginning balance (in shares) at Dec. 31, 2018	115,500,418	115,500,000
Beginning balance at Dec. 31, 2018	$ 410,634	$ 116	818,113	(1,019)	(406,576)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Equity component of convertible senior notes, net of issuance costs	180,887		180,887
Purchase of convertible senior notes capped call	(85,050)		(85,050)
Repurchase of common stock (in shares)		(504,000)
Repurchase of common stock	(20,000)	$ (1)	(19,999)
Issuance of common stock upon exercise of stock options and ESPP (in shares)		709,000
Issuance of common stock upon exercise of stock options and ESPP	5,820	$ 1	5,819
Net issuance of common stock for settlement of RSUs (in shares)		2,451,000
Net issuance of common stock for settlement of RSUs	(76,042)	$ 2	(76,044)
Issuance of common stock in connection with acquisition (in shares)		41,000
Issuance of common stock in connection with acquisition	1,160	$ 0	1,160
Share-based compensation expense	15,038		15,038
Other comprehensive income	119			119
Net loss	(4,318)				(4,318)
Beginning balance at Mar. 31, 2019	$ 428,137	$ 118	$ 839,924	$ (900)	$ (411,005)
Common stock, ending balance (in shares) at Mar. 31, 2019	118,196,707	118,197,000

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Cash flows from operating activities
Net loss	$ (4,318)	$ (2,617)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization expense	6,785	5,217
Share-based compensation expense	15,038	11,642
Amortization of debt discount and issuance costs	4,005	0
Operating lease expense, net of accretion	1,049	0
Other non-cash items	(44)	(41)
Change in assets and liabilities:
Accounts receivable	4,024	2,783
Prepaid expenses and other current assets	(11,522)	(7,894)
Other assets	(1,166)	(506)
Accounts payable	(1,836)	(3,068)
Deferred revenue	8,858	5,185
Accrued liabilities	216	(4,286)
Other liabilities	(3,148)	138
Net cash provided by operating activities	17,941	6,553
Cash flows from investing activities
Purchases of marketable securities	(21,572)	(12,511)
Maturities of marketable securities	48,805	21,630
Purchases of property and equipment	(14,060)	(4,883)
Net cash provided by investing activities	13,173	4,236
Cash flows from financing activities
Common stock issued under stock plans, net	6,982	5,222
Payment of taxes related to the net share settlement of equity awards	(76,044)	(35,640)
Proceeds from issuance of convertible senior notes, net of issuance costs	682,594	0
Purchase of convertible senior notes capped call	(85,050)	0
Repurchase of common stock	(20,000)	0
Net cash provided by (used in) financing activities	508,482	(30,418)
Net increase (decrease) in cash, cash equivalents and restricted cash	539,596	(19,629)
Cash, cash equivalents and restricted cash, beginning of period	375,945	126,963
Cash, cash equivalents and restricted cash, end of period	915,541	107,334
Supplemental cash flow data:
Interest	0	19
Income taxes	626	503
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	1,126	0
Non-cash investing activities:
Accrued purchases of long-lived assets	$ 5,127	$ 3,204

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - Reconciliation of cash, cash equivalents and restricted cash - USD ($) $ in Thousands	Mar. 31, 2019	Mar. 31, 2018
Statement of Cash Flows [Abstract]
Cash and cash equivalents	$ 914,500	$ 106,827
Cash and cash equivalents	121	84
Restricted cash included in other assets	920	423
Total cash, cash equivalents and restricted cash	$ 915,541	$ 107,334

Background and Basis of Presentation	3 Months Ended
Background and Basis of Presentation	Mar. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Background and Basis of Presentation	Background and Basis of Presentation Company and Background Chegg, Inc. (Chegg, the Company, we, us, or our), headquartered in Santa Clara, California, was incorporated as a Delaware corporation in July 2005. Chegg is a smarter way to student. As the leading direct-to-student learning platform, we strive to improve educational outcomes by putting the student first in all our decisions. We support students on their journey from high school to college and into their career with tools designed to help them pass their test, pass their class, and save money on required materials. Our services are available online, anytime and anywhere, so we can reach students when they need us most. Basis of Presentation The accompanying condensed consolidated balance sheet as of March 31, 2019, the condensed consolidated statements of operations, the condensed consolidated statements of comprehensive loss, the condensed consolidated statements of stockholder's equity, and the condensed consolidated statements of cash flows for the three months ended March 31, 2019 and 2018 and the related footnote disclosures are unaudited. In the opinion of management, the accompanying unaudited condensed consolidated financial statements contain all adjustments, including normal recurring adjustments, necessary to present fairly our financial position as of March 31, 2019, our results of operations, stockholder's equity, and cash flows for the three months ended March 31, 2019 and 2018. Our results of operations, stockholder's equity, and cash flows for the three months ended March 31, 2019 are not necessarily indicative of the results to be expected for the full year. We operate in a single segment. Our fiscal year ends on December 31 and in this report we refer to the year ended December 31, 2018 as 2018. The condensed consolidated financial statements and related financial information should be read in conjunction with the audited consolidated financial statements and the related notes thereto that are included in our Annual Report on Form 10-K for the year ended December 31, 2018 (the Annual Report on Form 10-K) filed with the U.S. Securities and Exchange Commission (SEC). Except for our policies on leases and convertible senior notes, there have been no material changes to our significant accounting policies as compared to the significant accounting policies described in our Annual Report on Form 10-K. Leases We determine if an arrangement is a lease at inception. Operating leases are included in operating lease right of use (ROU) assets, operating lease liabilities within current liabilities, and operating lease liabilities within long-term liabilities on our condensed consolidated balance sheet. Operating lease ROU assets and operating lease liabilities are recognized based on the present value of the future minimum lease payments over the lease term at commencement date. Our leases do not provide an implicit rate and therefore we use our incremental borrowing rate based on the information available at commencement date in determining the present value of future minimum lease payments. Our lease terms may include options to extend or terminate the lease when it is reasonably certain that we will exercise such options. We do not record leases on our condensed consolidated balance sheet with a term of one year or less. We do not separate lease and non-lease components but rather account for each separate component as a single lease component for all underlying classes of assets. Some of our leases include payments that are dependent on an index, such as the Consumer Price Index (CPI), and our minimum lease payments include payments based on the index at inception with any future changes in such indices recognized as an expense in the period of change. Where leases contain escalation clauses, rent abatements, or concessions, such as rent holidays and landlord or tenant incentives or allowances, we apply them in the determination of straight-line operating lease cost over the lease term. Operating lease cost for minimum lease payments is recognized on a straight-line basis over the lease term. Convertible Senior Notes, net In March 2019, we issued $700 million in aggregate principal amount of 0.125% convertible senior notes due in 2025 (2025 notes) and in April 2018, we issued $345 million in aggregate principal amount of 0.25% convertible senior notes due in 2023 (2023 notes). Collectively, the 2025 notes and 2023 notes are referred to as the “notes.” In accounting for their issuance, we separated the notes into liability and equity components. The carrying amount of the liability component was calculated by measuring the fair value of similar liabilities that do not have an associated convertible feature. The carrying amount of the equity component representing the conversion option was determined by deducting the carrying amount of the liability component from the par value of the notes. The difference represents the debt discount, recorded as a reduction of the convertible senior notes on our condensed consolidated balance sheet, and is amortized to interest expense over the term of the notes using the effective interest rate method. The equity component is not remeasured as long as it continues to meet the conditions for equity classification. In accounting for the issuance costs related to the notes, we allocated the total amount of issuance costs incurred to liability and equity components based on their relative values. Issuance costs attributable to the liability component are being amortized on a straight-line basis, which approximates the effective interest rate method, to interest expense over the term of the notes. The issuance costs attributable to the equity component are recorded as a reduction of the equity component within additional paid-in capital. Use of Estimates The preparation of financial statements in conformity with generally accepted accounting principles in the United States (U.S. GAAP) requires management to make estimates, judgments, and assumptions that affect the reported amounts of assets and liabilities; the disclosure of contingent liabilities at the date of the financial statements; and the reported amounts of revenues and expenses during the reporting periods. Significant estimates, assumptions, and judgments are used for, but not limited to: revenue recognition, recoverability of accounts receivable, restructuring charges (credits), share-based compensation expense including estimated forfeitures, accounting for income taxes, useful lives assigned to long-lived assets for depreciation and amortization, impairment of goodwill and long-lived assets, the valuation of acquired intangible assets, the valuation of our convertible senior notes, and operating lease ROU assets and operating lease liabilities. We base our estimates on historical experience, knowledge of current business conditions, and various other factors we believe to be reasonable under the circumstances. These estimates are based on management’s knowledge about current events and expectations about actions we may undertake in the future. Actual results could differ from these estimates, and such differences could be material to our financial position and results of operations. Recent Accounting Pronouncements Recently Issued Accounting Pronouncements Not Yet Adopted In August 2018, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) 2018-15, Intangibles—Goodwill and Other—Internal-Use Software (Subtopic 350-40): Customer's Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract. ASU 2018-15 aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with existing guidance contained within subtopic 350-40 to develop or obtain internal-use software. Early adoption is permitted and the guidance allows for a retrospective or prospective application. The guidance is effective for annual periods beginning after December 15, 2019, and we are currently in the process of evaluating the impact of this guidance. In July 2018, the FASB issued ASU 2018-09, Codification Improvements. ASU 2018-09 provides updates for technical corrections, clarifications, and other minor improvements to a wide variety of topics in the ASC. The transition method of adoption is dependent on the ASC topic impacted by this guidance. Additionally, some of the ASC topic updates are effective upon issuance of ASU 2018-09 and some of the ASC topic updates are effective at a future date. The ASC topic updates effective upon issuance of ASU 2018-09 do not impact our accounting for the respective ASC topics. For those ASC topic updates effective at a future date, we are currently in the process of evaluating the impact of this guidance update. Recently Adopted Accounting Pronouncements The FASB has issued four ASUs related to Accounting Standards Codification (ASC) 842. In March 2019, the FASB issued ASU 2019-01, Leases (Topic 842): Codification Improvements. In July 2018, the FASB issued ASU 2018-11, Leases (Topic 842): Targeted Improvements and ASU 2018-10, Codification Improvements to Topic 842, Leases. In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842). ASC 842 requires an entity to recognize a ROU asset and lease liability for all leases with terms of more than 12 months. Recognition, measurement, and presentation of expenses will depend on classification as a finance or operating lease. The amendments in this update also require certain quantitative and qualitative disclosures about leasing arrangements. We have adopted ASC 842 on January 1, 2019 and have elected the transition method of adoption that allows for a modified retrospective adoption with a cumulative-effect adjustment to the opening balance of accumulated deficit and recorded an immaterial decrease to our opening balance of accumulated deficit. As a result, we have not changed previously disclosed amounts or provided additional disclosures for comparative periods. We initially recorded ROU assets of $17.2 million and lease liabilities of $21.1 million on our condensed consolidated balance sheet. ASC 842 does not have a material impact to our condensed consolidated statement of operations. We have elected a package of transition practical expedients which include not reassessing whether any expired or existing contracts are or contain leases, not reassessing the lease classification of expired or existing leases, and not reassessing initial direct costs for existing leases. We have also elected a practical expedient to not separate lease and non-lease components. We did not elect the practical expedient to use hindsight in determining our lease terms or assessing impairment of our ROU assets. See Note 8. Leases for more information.

Revenues

3 Months Ended

Mar. 31, 2019

Revenue from Contract with Customer [Abstract]

Revenues

Revenue Recognition

Revenues are recognized when control of the promised goods or services is transferred to our customers, in an amount that reflects the consideration we expect to be entitled to in exchange for those goods or services. The majority of our revenues are recognized over time as services are performed, with certain revenues, most significantly the revenue share we earn from our print textbook partners, being recognized at the point in time when print textbooks are shipped to students.

The following table sets forth our total net revenues for the periods shown disaggregated for our Chegg Services and Required Materials product lines (in thousands, except percentages):



	Three Months Ended March 31,				Change
	2019		2018		$		%
Chegg Services	$	75,292	$	56,277	$	19,015	34	%
Required Materials	22,117		20,672		1,445		7	%
Total net revenues	$	97,409	$	76,949	$	20,460	27	%

During the three months ended March 31, 2019, we recognized $12.4 million of revenues that were included in our deferred revenue balance as of December 31, 2018. During the three months ended March 31, 2019, there was an immaterial amount of revenues recognized from performance obligations satisfied in previous periods. The aggregate amount of unsatisfied performance obligations is approximately $29.0 million as of March 31, 2019, of which substantially all is expected to be recognized into revenues over the next year and the remainder within three years.

Contract Balances

The following table presents our accounts receivable, net and deferred revenue balances (in thousands, except percentages):



					Change
	March 31, 2019		December 31, 2018		$			%
Accounts receivable, net	$	8,870	$	12,733	$	(3,863	)	(30	)%
Deferred revenue	$	26,276	$	17,418	$	8,858		51	%

During the three months ended March 31, 2019, our accounts receivable, net balance decreased by $3.9 million, or 30%, primarily due to an improvement in cash collections. During the three months ended March 31, 2019, our deferred revenue balance increased by $8.9 million, or 51%, primarily due to increased bookings for our Chegg Study service and eTextbook rentals driven by the seasonality of our business as well as the deferred variable consideration. Our contract assets balance was immaterial as of March 31, 2019 and December 31, 2018.

Net Loss Per Share

3 Months Ended

Mar. 31, 2019

Earnings Per Share [Abstract]

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 stock options, warrants, restricted stock units (RSUs), performance-based restricted stock units (PSUs), and shares related to convertible senior notes, to the extent dilutive. Basic and diluted net loss per share was the same for each period presented as the inclusion of all potential common shares outstanding would have been anti-dilutive.

The following table sets forth the computation of historical basic and diluted net loss per share (in thousands, except per share amounts):



	Three Months Ended March 31,
	2019			2018
Numerator:
Net loss	$	(4,318	)	$	(2,617	)
Denominator:
Weighted average shares used to compute net loss per share, basic and diluted	116,730			110,904

Net loss per share, basic and diluted	$	(0.04	)	$	(0.02	)

The following potential weighted-average shares of common stock outstanding were excluded from the computation of diluted net loss per share because including them would have been anti-dilutive (in thousands):



	Three Months Ended March 31,
	2019	2018
Options to purchase common stock	3,258	4,079
RSUs and PSUs	6,732	8,791
Shares related to convertible senior notes	3,332	—
Employee stock purchase plan	41	—
Total common stock equivalents	13,363	12,870

Shares related to convertible senior notes represents the anti-dilutive impact of our issuance of $345 million in aggregate principal amount of our 0.25% convertible senior notes due in 2023 (2023 notes) as the average price of our common stock during the three months ended March 31, 2019 was higher than the conversion price of $26.95. While these shares are anti-dilutive during the three months ended March 31, 2019, they may be dilutive in periods we report net income. However, as a result of the capped call transactions described in Note 7, there will be no economic dilution from the 2023 notes up to $40.68, as exercise of the capped call instruments will reduce any dilution from the notes that would have otherwise occurred when the average price of our common stock exceeds the conversion price. None of the shares related to our issuance of $700 million in aggregate principal amount of our 0.125% convertible senior notes due in 2025 (2025 notes) were anti-dilutive during the three months ended March 31, 2019.

Cash and Cash Equivalents, and Investment

3 Months Ended

Mar. 31, 2019

Cash and Cash Equivalents [Abstract]

Cash and Cash Equivalents, and Investment

Cash and Cash Equivalents, and Investments

The following table shows our cash and cash equivalents, and investments’ adjusted cost, net unrealized gain/(loss) and fair value as of March 31, 2019 and December 31, 2018 (in thousands):



	March 31, 2019							December 31, 2018
	Cost		Net Unrealized Gain/(Loss)			Fair Value		Cost		Net Unrealized Loss			Fair Value
Cash and cash equivalents:
Cash	$	279,928	$	—		$	279,928	$	351,345	$	—		$	351,345
Money market funds	613,210		—			613,210		5,052		—			5,052
Commercial paper	21,369		(7		)	21,362		18,267		—			18,267
Total cash and cash equivalents	$	914,507	$	(7	)	$	914,500	$	374,664	$	—		$	374,664
Short-term investments:
Commercial paper	$	28,360	$	(3	)	$	28,357	$	40,500	$	(12	)	$	40,488
Corporate securities	26,235		(3		)	26,232		38,616		(87		)	38,529
U.S. treasury securities	15,488		3			15,491		14,333		(5		)	14,328
Total short-term investments	$	70,083	$	(3	)	$	70,080	$	93,449	$	(104	)	$	93,345
Long-term investments:
Corporate securities	$	10,842	$	56		$	10,898	$	14,429	$	(5	)	$	14,424
U.S. treasury securities	1,633		2			1,635		1,630		(2		)	1,628
Total long-term investments	$	12,475	$	58		$	12,533	$	16,059	$	(7	)	$	16,052

The adjusted cost and fair value of available-for-sale investments as of March 31, 2019 by contractual maturity were as follows (in thousands):



	Cost		Fair Value
Due in 1 year or less	$	91,452	$	91,442
Due in 1-2 years	12,475		12,533
Investments not due at a single maturity date	613,210		613,210
Total	$	717,137	$	717,185

Investments not due at a single maturity date in the preceding table consist of money market fund deposits.

As of March 31, 2019, we considered the declines in market value of our investment portfolio to be temporary in nature and did not consider any of our investments to be other-than-temporarily impaired. We typically invest in highly-rated securities with a minimum credit rating of A- and a weighted average maturity of one month, and our investment policy generally limits the amount of credit exposure to any one issuer. The policy requires investments generally to be investment grade, with the primary objective of preserving capital and maintaining liquidity. Fair values were determined for each individual security in the investment portfolio. When evaluating an investment for other-than-temporary impairment, we review factors such as the length of time and extent to which fair value has been below its cost basis, the financial condition of the issuer and any changes thereto, changes in market interest rates and our intent to sell, or whether it is more likely than not it will be required to sell, the investment before recovery of the investment’s cost basis. During the three months ended March 31, 2019 and 2018, we did not recognize any impairment charges.

Restricted Cash

As of March 31, 2019 and December 31, 2018, we had approximately $1.0 million and $1.3 million, respectively, of restricted cash that consists of security deposits for our corporate offices. These amounts are classified in either other current assets or other assets on our condensed consolidated balance sheets based on the remaining term of the lease from the balance sheet dates.

Strategic Investments

In October 2018, we completed an investment of $10.0 million in WayUp, Inc., a U.S.-based job site and mobile application for college students and recent graduates. Additionally, we previously invested $3.0 million in a foreign entity to explore expanding our reach internationally. We did not record other-than-temporary impairment charges on our investments during the three months ended March 31, 2019 and 2018, as there were no significant identified events or changes in circumstances that would be considered an indicator for impairment. There were no observable price changes in orderly transactions for the identical or a similar investment of the same issuer during the three months ended March 31, 2019 and 2018.

Fair Value Measurement

3 Months Ended

Mar. 31, 2019

Fair Value Disclosures [Abstract]

Fair Value Measurement

We have established a fair value hierarchy used to determine the fair value of our financial instruments as follows:

Level 1—Inputs are unadjusted quoted prices in active markets for identical assets or liabilities.

Level 2—Inputs are quoted prices for similar assets and liabilities in active markets or inputs that are observable for the assets or liabilities, either directly or indirectly through market corroboration, for substantially the full term of the financial instruments.

Level 3—Inputs are unobservable inputs based on our own assumptions used to measure assets and liabilities at fair value; the inputs require significant management judgment or estimation.

A financial instrument’s classification within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement.

Financial instruments measured and recorded at fair value on a recurring basis as of March 31, 2019 and December 31, 2018 are classified based on the valuation technique level in the tables below (in thousands):



	March 31, 2019
	Total		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)
Assets:
Cash equivalents:
Money market funds	$	613,210	$	613,210	$	—
Commercial paper	21,362		—		21,362
Short-term investments:
Commercial paper	28,357		—		28,357
Corporate securities	26,232		—		26,232
U.S. treasury securities	15,491		15,491		—
Long-term investments:
Corporate securities	10,898		—		10,898
U.S. treasury securities	1,635		1,635		—
Total assets measured and recorded at fair value	$	717,185	$	630,336	$	86,849



	December 31, 2018
	Total		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)
Assets:
Cash equivalents:
Money market funds	$	5,052	$	5,052	$	—
Commercial paper	18,267		—		18,267
Short-term investments:	—
Commercial paper	40,488		—		40,488
Corporate securities	38,529		—		38,529
U.S. treasury securities	14,328		14,328		—
Long-term investments:
Corporate securities	14,424		—		14,424
U.S. treasury securities	1,628		1,628		—
Total assets measured and recorded at fair value	$	132,716	$	21,008	$	111,708

We value our marketable securities based on quoted prices in active markets for identical assets (Level 1 inputs) or inputs other than quoted prices that are observable either directly or indirectly (Level 2 inputs) in determining fair value. Other than our money market funds and U.S. treasury securities, we classify our fixed income available-for-sale securities as having Level 2 inputs. The valuation techniques used to measure the fair value of our financial instruments having Level 2 inputs were derived from non-binding market consensus prices that are corroborated by observable market data, quoted market prices for similar instruments, or pricing models such as discounted cash flow techniques. We do not hold any marketable securities valued with a Level 3 input.

The methods described above may produce a fair value calculation that may not be indicative of net realizable value or reflective of future fair values. Furthermore, while we believe our valuation methods are appropriate and consistent with other market participants, the use of different methodologies or assumptions to determine the fair value of certain financial instruments could result in a different fair value measurement at the reporting date.

Financial Instruments Not Recorded at Fair Value on a Recurring Basis

We report our financial instruments at fair value with the exception of the 2023 notes and 2025 notes. Collectively, the 2025 notes and 2023 notes are referred to as the “notes.” The estimated fair value of the notes was determined based on the trading price of the notes as of the last day of trading for the period. We consider the fair value of the notes to be a Level 2 measurement due to the limited trading activity. For further information on the notes see Note 7.

The carrying amounts and estimated fair values of the notes as of March 31, 2019 and December 31, 2018 are as follows (in thousands):



	March 31, 2019				December 31, 2018
	Carrying Amount		Estimated Fair Value		Carrying Amount		Estimated Fair Value
2025 notes	$	502,252	$	693,945	$	—	$	—
2023 notes	$	287,128	$	520,108	$	283,668	$	416,156
Convertible senior notes, net	$	789,380	$	1,214,053	$	283,668	$	416,156

The carrying amount of the 2025 notes and 2023 notes as of March 31, 2019 was net of unamortized debt discount of $185.0 million and $51.7 million, respectively, and unamortized issuance costs of $12.8 million and $6.1 million, respectively. The carrying amount of the 2023 notes as of December 31, 2018 was net of unamortized debt discount of $54.8 million and unamortized issuance costs of $6.5 million.

- Definition

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

+ References + Details

Goodwill and Intangible Assets

3 Months Ended

Mar. 31, 2019

Goodwill and Intangible Assets Disclosure [Abstract]

Goodwill and Intangible Assets

Goodwill consists of the following (in thousands):



	March 31, 2019			December 31, 2018
Beginning balance	$	149,524		$	125,272
Additions due to acquisitions	—			24,673
Foreign currency translation adjustment	(43		)	(421		)
Ending balance	$	149,481		$	149,524

Intangible assets as of March 31, 2019 and December 31, 2018 consist of the following (in thousands, except weighted-average amortization period):



	March 31, 2019
	Weighted-Average Amortization Period	Gross Carrying Amount			Accumulated Amortization			Net Carrying Amount
Developed technologies and content library	71	$	31,667		$	(14,821	)	$	16,846
Customer lists	47	9,970			(7,188		)	2,782
Trade names	44	6,113			(5,162		)	951
Non-compete agreements	31	2,018			(1,801		)	217
Indefinite-lived trade name	—	3,600			—			3,600
Foreign currency translation adjustment	—	(299		)	—			(299		)
Total intangible assets	61	$	53,069		$	(28,972	)	$	24,097



	December 31, 2018
	Weighted-Average Amortization Period	Gross Carrying Amount			Accumulated Amortization			Net Carrying Amount
Developed technologies and content library	71	$	31,667		$	(13,737	)	$	17,930
Customer lists	47	9,970			(6,847		)	3,123
Trade names	44	6,113			(4,863		)	1,250
Non-compete agreements	31	2,018			(1,735		)	283
Indefinite-lived trade name	—	3,600			—			3,600
Foreign currency translation adjustment	—	(271		)	—			(271		)
Total intangible assets	61	$	53,097		$	(27,182	)	$	25,915

During the three months ended March 31, 2019 and 2018, amortization expense related to our acquired intangible assets totaled approximately $1.8 million and $1.4 million, respectively.

As of March 31, 2019, the estimated future amortization expense related to our finite-lived intangible assets is as follows (in thousands):



Remaining nine months of 2019	$	4,658
2020	4,816
2021	3,423
2022	2,943
2023	2,276
Thereafter	2,381
Total	$	20,497

Convertible Senior Notes

3 Months Ended

Mar. 31, 2019

Debt Disclosure [Abstract]

Convertible Senior Notes

In March 2019, we issued $700 million in aggregate principal amount of 0.125% convertible senior notes due in 2025 (2025 notes). In April 2018, we issued $345 million in aggregate principal amount of 0.25% convertible senior notes due in 2023 (2023 notes). The aggregate principal amount of the 2023 notes includes $45 million from the initial purchasers fully exercising their option to purchase additional notes. Collectively, the 2025 notes and 2023 notes are referred to as the “notes.” The notes were issued in private placements to qualified institutional buyers pursuant to Rule 144A of the Securities Act of 1933, as amended.

The total net proceeds from the notes are as follows (in thousands):



	2025 Notes			2023 Notes
Principal amount	$	700,000		$	345,000
Less initial purchasers’ discount	(16,625		)	(8,625		)
Less other issuance costs	(781		)	(757		)
Net proceeds	$	682,594		$	335,618

The notes are our senior, unsecured obligations and are governed by indenture agreements by and between us and Wells Fargo Bank, National Association, as Trustee (the indentures). The 2025 notes bear interest of 0.125% per year which is payable semi-annually in arrears on March 15 and September 15 of each year, beginning on September 15, 2019. The 2025 notes will mature on March 15, 2025 (the 2025 notes maturity date), unless repurchased, redeemed or converted in accordance with their terms prior to such date. The 2023 notes bear interest of 0.25% per year which is payable semi-annually in arrears on May 15 and November 15 of each year, beginning on November 15, 2018. The 2023 notes will mature on May 15, 2023 (the 2023 notes maturity date), unless repurchased, redeemed or converted in accordance with their terms prior to such date.

Each $1,000 principal amount of the 2025 notes will initially be convertible into 19.3956 shares of our common stock. This is equivalent to an initial conversion price of approximately $51.56 per share, which is subject to adjustment in certain circumstances. Each $1,000 principal amount of the 2023 notes will initially be convertible into 37.1051 shares of our common stock. This is equivalent to an initial conversion price of approximately $26.95 per share, which is subject to adjustment in certain circumstances.

Prior to the close of business on the business day immediately preceding December 15, 2024 for the 2025 notes and February 15, 2023 for the 2023 notes, the notes are convertible at the option of holders only upon satisfaction of the following circumstances:

•

during any calendar quarter commencing after the calendar quarter ending on June 30, 2019 for the 2025 notes and June 30, 2018 for the 2023 notes, if the last reported sale price of our common stock for at least 20 trading days (whether or not consecutive) during a period of 30 consecutive trading days ending on, and including, the last trading day of the immediately preceding calendar quarter is greater than or equal to 130% of the respective conversion price for the notes on each applicable trading day;


•	during the five business day period after any ten consecutive trading day period (the measurement period) in which the trading price per $1,000 principal amount of notes for each trading day of the measurement period was less than 98% of the product of the last reported sale price of our common stock and the conversion rate on each such trading day;


•	if we call any or all of the notes for redemption, at any time prior to the close of business on the second scheduled trading day immediately preceding the redemption date; or


•	upon the occurrence of certain specified corporate events described in the indentures.

On or after December 15, 2024 for the 2025 notes and February 15, 2023 for the 2023 notes until the close of business on the second scheduled trading day immediately preceding the respective maturity dates, holders may convert their notes at any time, regardless of the foregoing circumstances. Upon conversion, the notes may be settled in shares of our common stock, cash or a combination of cash and shares of our common stock, at our election.

If we undergo a fundamental change, as defined in the indentures, prior to the respective maturity dates, subject to certain conditions, holders of the notes may require us to repurchase for cash all or any portion of their notes at a repurchase price equal to 100% of the principal amount of the notes to be repurchased, plus accrued and unpaid interest to, but excluding, the fundamental change repurchase date. In addition, if specific corporate events, described in the indentures, occur prior to the respective maturity dates, we will also increase the conversion rate for a holder who elects to convert their notes in connection with such specified corporate events.

During the three months ended March 31, 2019, the conditions allowing holders of the 2025 notes to convert have not been met and are therefore not convertible during the three months ended March 31, 2019. During the three months ended March 31, 2019, the conditions allowing holders of the 2023 notes to convert have been met and are therefore convertible during the three months ended March 31, 2019. None of the holders of the 2023 notes elected to convert their notes into shares of our common stock during the three months ended March 31, 2019.

In accounting for the issuance of the notes, we separated the notes into liability and equity components. The carrying amount of the liability components for the 2025 notes and 2023 notes of approximately $514.5 million and $280.8 million, respectively, was calculated by measuring the fair value of similar debt instruments that do not have an associated convertible feature. The carrying amount of the equity components for the 2025 notes and 2023 notes of approximately $185.5 million and $64.2 million, respectively, representing the conversion option, was determined by deducting the carrying amount of the liability components from the principal amount of the notes. This difference between the principal amount of the notes and the liability components represents the debt discount, presented as a reduction to the notes on our condensed consolidated balance sheet, and is amortized to interest expense using the effective interest method over the remaining term of the notes. The equity components of the notes are included in additional paid-in capital on our condensed consolidated balance sheet and is not remeasured as long as it continues to meet the conditions for equity classification.

We incurred issuance costs related to the 2025 notes of approximately $17.4 million, consisting of the initial purchasers' discount of $16.6 million and other issuance costs of approximately $0.8 million. We incurred issuance costs related to the 2023 notes of approximately $9.4 million, consisting of the initial purchasers' discount of $8.6 million and other issuance costs of approximately $0.8 million. In accounting for the issuance costs, we allocated the total amount incurred to the liability and equity components using the same proportions determined above for the notes. Transaction costs attributable to the liability components for the 2025 notes and 2023 notes of approximately $12.8 million and $7.6 million, respectively, were recorded as debt issuance cost, presented as a reduction to the notes on our condensed consolidated balance sheet, and are amortized to interest expense using the effective interest method over the term of the notes. The issuance costs attributable to the equity components for the 2025 notes and 2023 notes were approximately $4.6 million and $1.7 million, respectively, and were recorded as a reduction to the equity component included in additional paid-in capital.

The net carrying amount of the liability component of the notes is as follows (in thousands):



	March 31, 2019						December 31, 2018
	2025 Notes			2023 Notes			2023 Notes
Principal	$	700,000		$	345,000		$	345,000
Unamortized debt discount	(184,990		)	(51,725		)	(54,817		)
Unamortized issuance costs	(12,758		)	(6,147		)	(6,515		)
Net carrying amount	$	502,252		$	287,128		$	283,668

The net carrying amount of the equity component of the notes is as follows (in thousands):



	March 31, 2019						December 31, 2018
	2025 Notes			2023 Notes			2023 Notes
Debt discount for conversion option	$	185,500		$	64,193		$	64,193
Issuance costs	(4,613		)	(1,749		)	(1,749		)
Net carrying amount	$	180,887		$	62,444		$	62,444

As of March 31, 2019, the remaining lives of the 2025 notes and 2023 notes are approximately 6.0 and 4.1 years, respectively, and are classified as long-term debt.

Based on the closing price of our common stock of $38.12 on March 31, 2019, the if-converted value of the 2025 notes was approximately $517.6 million which is less than the principal amount of $700 million by approximately $182.4 million and the if-converted value of the 2023 notes was approximately $488.0 million which exceeds the principal amount of $345 million by approximately $143.0 million.

The effective interest rate of the liability components for the 2025 notes and 2023 notes are 5.4% and 4.34%, respectively, and is based on the interest rate of similar debt instruments, at the time of our offering, that do not have associated convertible features. The following table sets forth the total interest expense recognized related to the notes (in thousands):



	Three Months Ended March 31, 2019
	2025 Notes		2023 Notes
Contractual interest expense	$	14	$	213
Amortization of debt discount	510		3,091
Amortization of issuance costs	35		369
Total interest expense	$	559	$	3,673

Capped Call Transactions

Concurrently with the offering of the 2025 notes and 2023 notes, we used $85.1 million and $39.2 million, respectively, of the net proceeds to enter into privately negotiated capped call transactions which are expected to generally reduce or offset potential dilution to holders of our common stock upon conversion of the notes and/or offset the potential cash payments we would be required to make in excess of the principal amount of any converted notes. The capped call transactions cover 13,576,920 and 12,801,260 shares of our common stock for the 2025 notes and 2023 notes, respectively, and are intended to effectively increase the overall conversion price from $51.56 to $79.32 per share for the 2025 notes and $26.95 to $40.68 per share for the 2023 notes. As these transactions meet certain accounting criteria, they are recorded in stockholders’ equity as a reduction of additional paid-in capital on our condensed consolidated balance sheet and are not accounted for as derivatives. The fair value of the capped call instrument is not remeasured each reporting period. The cost of the capped call is not expected to be deductible for tax purposes.

Impact to Earnings per Share

The notes will have no impact to diluted earnings per share until the average price of Chegg’s common stock exceeds the conversion price for the 2025 notes and 2023 notes of $51.56 and $26.95 per share, respectively, because we intend to settle the principal amount of the notes in cash upon conversion. Under the treasury stock method, in periods we report net income, we are required to include the effect of additional shares that may be issued under the notes when the average price of our common stock exceeds the conversion price. However, as a result of the capped call transactions described above, there will be no economic dilution from the 2025 notes and 2023 notes up to $79.32 and $40.68, respectively, as exercise of the capped call instruments will reduce any dilution from the notes that would have otherwise occurred when the average price of our common stock exceeds the conversion price.

Leases

3 Months Ended

Mar. 31, 2019

Leases [Abstract]

Leases

We have operating leases for corporate offices worldwide, which expire at various dates through 2024. Our primary operating lease commitments at March 31, 2019 are related to our corporate headquarters in Santa Clara, California. We have additional offices in California, Oregon, Georgia and New York in the United States and internationally in India, Israel and Germany.

As of March 31, 2019, we had operating lease ROU assets of $15.9 million and operating lease liabilities of $20.1 million. As of March 31, 2019, we do not have finance leases recorded on our condensed consolidated balance sheet. As of March 31, 2019, our weighted average remaining lease term was 4.3 years. During the three months ended March 31, 2019, our weighted average discount rate was 4.7%.

Operating lease expense was approximately $1.3 million during the three months ended March 31, 2019. Variable lease cost was immaterial during the three months ended March 31, 2019. We did not record any sublease income or short term lease cost during the three months ended March 31, 2019.

The aggregate future minimum lease payments and reconciliation to lease liabilities as of March 31, 2019, are as follows (in thousands):



	March 31, 2019
Remaining nine months of 2019	$	4,101
2020	5,200
2021	4,724
2022	3,948
2023	3,424
Thereafter	788
Total future minimum lease payments	22,185
Less imputed interest	(2,121		)
Total lease liabilities	$	20,064

The aggregate future minimum lease payments as of December 31, 2018, are as follows (in thousands):



	December 31, 2018
2019	$	5,222
2020	5,251
2021	4,775
2022	3,999
2023	3,421
Thereafter	788
Total	$	23,456

Commitments and Contingencies	3 Months Ended
Commitments and Contingencies	Mar. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies From time to time, third parties may assert patent infringement claims against us in the form of letters, litigation, or other forms of communication. In addition, we may from time to time be subject to other legal proceedings and claims in the ordinary course of business, including claims of alleged infringement of trademarks, copyrights, and other intellectual property rights; employment claims; and general contract or other claims. We may also, from time to time, be subject to various legal or government claims, disputes, or investigations. Such matters may include, but not be limited to, claims, disputes, or investigations related to warranty, refund, breach of contract, employment, intellectual property, government regulation, or compliance or other matters. On September 27, 2018 a purported securities class action captioned Shah v. Chegg, Inc. et. al. (Case No. 3:18-cv-05956-CRB) was filed in the U.S. District Court for the Northern District of California against us and our CEO. The complaint was filed by a purported Company shareholder and alleges claims under Sections 10(b) and 20(a) of the Securities Exchange Act of 1934, as amended, and SEC Rule 10b-5, based on allegedly misleading statements regarding the Company’s security measures to protect users’ data and related internal controls and procedures, as well as our second quarter 2018 financial results. The suit is purportedly brought on behalf of purchasers of our securities between July 30, 2018 and September 25, 2018. The complaint seeks unspecified compensatory damages, as well as interest, costs and attorneys’ fees. On November 15, 2018, a second purported securities class action captioned Kurland v. Chegg, Inc. et al. (Case No. 3:18-cv-06714-CRB) was filed in the U.S. District Court for the Northern District of California against us, our CEO, and our CFO. The Shah and Kurland actions contain similar allegations, assert similar claims, and seek similar relief, and on January 24, 2019, the Court consolidated the two actions. On March 29, 2019, the Plaintiffs filed a Lead Plaintiff's notice of Voluntary Dismissal Without Prejudice. NetSoc, LLC (“NetSoc”) filed a complaint for patent infringement against us in the U.S. District Court for the Southern District of New York on November 5, 2018. NetSoc alleges that our Chegg Tutors service infringes U.S. Patent No. 9,978,107 (“the ’107 Patent”). A responsive pleading was filed on February 19, 2019 and an initial status conference was held on March 1, 2019. The parties have been ordered to schedule mediation. The complaint seeks unspecified compensatory damages. We have not recorded any amounts related to the above matters, as we do not believe that a loss is probable in either matter. We are not aware of any other pending legal matters or claims, individually or in the aggregate, that are expected to have a material adverse impact on our consolidated financial position, results of operations or cash flows. However, our analysis of whether a claim may proceed to litigation cannot be predicted with certainty, nor can the results of litigation be predicted with certainty. Nevertheless, defending any of these actions, regardless of the outcome, may be costly, time consuming, distract management personnel and have a negative effect on our business. An adverse outcome in any of these actions, including a judgment or settlement, may cause a material adverse effect on our future business, operating results and/or financial condition.

Guarantees and Indemnifications	3 Months Ended
Guarantees and Indemnifications	Mar. 31, 2019
Guarantees And Indemnifications [Abstract]
Guarantees and Indemnifications	Guarantees and Indemnifications We have agreed to indemnify our directors and officers for certain events or occurrences, subject to certain limits, while such persons are or were serving at our request in such capacity. We may terminate the indemnification agreements with these persons upon termination of employment, but termination will not affect claims for indemnification related to events occurring prior to the effective date of termination. We have a directors’ and officers’ insurance policy that limits our potential exposure up to the limits of our insurance coverage. In addition, we also have other indemnification agreements with various vendors against certain claims, liabilities, losses, and damages. The maximum amount of potential future indemnification is unlimited. We believe the fair value of these indemnification agreements is minimal. We have not recorded any liabilities for these agreements as of March 31, 2019.

Stockholders' Equity

3 Months Ended

Mar. 31, 2019

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Stockholders' Equity

In conjunction with our 2025 notes offering in March 2019, we repurchased 504,286 shares of our common stock at an average price per share of $39.66.

Share-based Compensation Expense

Total share-based compensation expense recorded for employees and non-employees, is as follows (in thousands):



	Three Months Ended March 31,
	2019		2018
Cost of revenues	$	125	$	94
Research and development	4,917		4,133
Sales and marketing	1,808		1,589
General and administrative	8,188		5,826
Total share-based compensation expense	$	15,038	$	11,642

RSU and PSU Activity

Activity for RSUs and PSUs is as follows:



	RSUs and PSUs Outstanding
	Number of RSUs and PSUs Outstanding		Weighted Average Grant Date Fair Value
Balance at December 31, 2018	10,804,808		$	11.87
Granted	1,440,428		39.95
Released	(4,352,468	)	8.97
Canceled	(727,939	)	7.12
Balance at March 31, 2019	7,164,829		$	19.76

As of March 31, 2019, our total unrecognized share-based compensation expense related to RSUs and PSUs was approximately $98.1 million, which will be recognized over the remaining weighted-average vesting period of approximately 1.9 years.

Income Taxes	3 Months Ended
Income Taxes	Mar. 31, 2019
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes We recorded an income tax provision of approximately $0.6 million and $0.5 million during the three months ended March 31, 2019 and 2018, respectively, primarily due to state and foreign income tax expense.

Restructuring Charges

3 Months Ended

Mar. 31, 2019

Restructuring and Related Activities [Abstract]

Restructuring Charges

2017 Restructuring Plan

In January 2017, we entered into a strategic partnership with the National Research Center for College & University Admissions (NRCCUA) where they will assume responsibility for managing, renewing, and maintaining our existing university contracts and become the exclusive reseller of our digital marketing services for colleges and universities. As a result of this strategic partnership, approximately 55 employees in China and the United States supporting the sales and account support functions of our marketing services offerings were terminated. Costs incurred to date are expected to be fully paid within 1 month.

2015 Restructuring Plan

We recorded a reduction of $0.3 million to our 2015 Restructuring Plan liability related to our adoption of ASU 2016-02, Leases (Topic 842) during the three months ended March 31, 2019. Our 2015 Restructuring Plan is now complete.

The following table summarizes the activity related to the accrual for restructuring charges (in thousands):



	2017 Restructuring Plan						2015 Restructuring Plan
	Workforce Reduction Costs			Lease Termination and Other Costs			Lease Termination and Other Costs			Total
Balance at January 1, 2018	$	44		$	—		$	221		$	265
Restructuring charges	253			19			317			589
Cash payments	(151		)	(19		)	(218		)	(388		)
Write-offs	—			—			(18		)	(18		)
Balance at December 31, 2018	146			—			302			448
Cumulative-effect adjustment to accumulated deficit related to adoption of ASU 2016-02	—			—			(302		)	(302		)
Restructuring charges	22			—			—			22
Cash payments	(132		)	—			—			(132		)
Balance at March 31, 2019	$	36		$	—		$	—		$	36

Related-Party Transactions	3 Months Ended
Related-Party Transactions	Mar. 31, 2019
Related Party Transactions [Abstract]
Related-Party Transactions	Related-Party Transactions Our Chief Executive Officer is a member of the Board of Directors of Adobe Systems Incorporated (Adobe). During the three months ended March 31, 2019 and 2018, we had purchases of $1.0 million and $1.7 million, respectively, from Adobe. We had no revenues during the three months ended March 31, 2019 and $0.1 million of revenues during the three months ended March 31, 2018 from Adobe. We had an immaterial amount in payables as of March 31, 2019 and December 31, 2018 to Adobe. We had no outstanding receivables as of March 31, 2019 and December 31, 2018 from Adobe. One of our board members is also a member of the Board of Directors of Cengage Learning, Inc. (Cengage). During the three months ended March 31, 2019 and 2018, we had purchases of $9.1 million and $5.1 million, respectively, from Cengage. We had $1.2 million and $1.9 million of revenues during the three months ended March 31, 2019, respectively, from Cengage. We had $0.5 million and $0.1 million in payables as of March 31, 2019 and December 31, 2018, respectively, to Cengage. We had an immaterial amount of outstanding receivables as of March 31, 2019 and December 31, 2018 from Cengage. The immediate family of one of our board members is also a member of the Board of Directors of PayPal Holdings, Inc. (PayPal). During the three months ended March 31, 2019 and 2018, we incurred payment processing fees of $0.4 million to PayPal. One of our board members is also a member of the Board of Directors of Synack, Inc. (Synack). During the three months ended March 31, 2019, we had purchases of $0.3 million of services from Synack.

Subsequent Event	3 Months Ended
Subsequent Event	Mar. 31, 2019
Subsequent Events [Abstract]
Subsequent Event	Subsequent Event On April 3, 2019, in conjunction with our March 2019 issuance of the 2025 notes, we issued an additional $100 million of the 2025 notes from the initial purchasers fully exercising their option to purchase additional notes. We used approximately $12.2 million of the additional proceeds to pay for the cost of additional privately negotiated capped call transactions. The notes from this additional issuance and additional capped call transactions follow the same terms as disclosed in Note 7. Convertible Senior Notes.

Background and Basis of Presentation (Policies)	3 Months Ended
Background and Basis of Presentation (Policies)	Mar. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation The accompanying condensed consolidated balance sheet as of March 31, 2019, the condensed consolidated statements of operations, the condensed consolidated statements of comprehensive loss, the condensed consolidated statements of stockholder's equity, and the condensed consolidated statements of cash flows for the three months ended March 31, 2019 and 2018 and the related footnote disclosures are unaudited. In the opinion of management, the accompanying unaudited condensed consolidated financial statements contain all adjustments, including normal recurring adjustments, necessary to present fairly our financial position as of March 31, 2019, our results of operations, stockholder's equity, and cash flows for the three months ended March 31, 2019 and 2018. Our results of operations, stockholder's equity, and cash flows for the three months ended March 31, 2019 are not necessarily indicative of the results to be expected for the full year. We operate in a single segment. Our fiscal year ends on December 31 and in this report we refer to the year ended December 31, 2018 as 2018. The condensed consolidated financial statements and related financial information should be read in conjunction with the audited consolidated financial statements and the related notes thereto that are included in our Annual Report on Form 10-K for the year ended December 31, 2018 (the Annual Report on Form 10-K) filed with the U.S. Securities and Exchange Commission (SEC). Except for our policies on leases and convertible senior notes, there have been no material changes to our significant accounting policies as compared to the significant accounting policies described in our Annual Report on Form 10-K.
Leases	Leases We determine if an arrangement is a lease at inception. Operating leases are included in operating lease right of use (ROU) assets, operating lease liabilities within current liabilities, and operating lease liabilities within long-term liabilities on our condensed consolidated balance sheet. Operating lease ROU assets and operating lease liabilities are recognized based on the present value of the future minimum lease payments over the lease term at commencement date. Our leases do not provide an implicit rate and therefore we use our incremental borrowing rate based on the information available at commencement date in determining the present value of future minimum lease payments. Our lease terms may include options to extend or terminate the lease when it is reasonably certain that we will exercise such options. We do not record leases on our condensed consolidated balance sheet with a term of one year or less. We do not separate lease and non-lease components but rather account for each separate component as a single lease component for all underlying classes of assets. Some of our leases include payments that are dependent on an index, such as the Consumer Price Index (CPI), and our minimum lease payments include payments based on the index at inception with any future changes in such indices recognized as an expense in the period of change. Where leases contain escalation clauses, rent abatements, or concessions, such as rent holidays and landlord or tenant incentives or allowances, we apply them in the determination of straight-line operating lease cost over the lease term. Operating lease cost for minimum lease payments is recognized on a straight-line basis over the lease term.
Convertible Senior Notes, net	Convertible Senior Notes, net In March 2019, we issued $700 million in aggregate principal amount of 0.125% convertible senior notes due in 2025 (2025 notes) and in April 2018, we issued $345 million in aggregate principal amount of 0.25% convertible senior notes due in 2023 (2023 notes). Collectively, the 2025 notes and 2023 notes are referred to as the “notes.” In accounting for their issuance, we separated the notes into liability and equity components. The carrying amount of the liability component was calculated by measuring the fair value of similar liabilities that do not have an associated convertible feature. The carrying amount of the equity component representing the conversion option was determined by deducting the carrying amount of the liability component from the par value of the notes. The difference represents the debt discount, recorded as a reduction of the convertible senior notes on our condensed consolidated balance sheet, and is amortized to interest expense over the term of the notes using the effective interest rate method. The equity component is not remeasured as long as it continues to meet the conditions for equity classification. In accounting for the issuance costs related to the notes, we allocated the total amount of issuance costs incurred to liability and equity components based on their relative values. Issuance costs attributable to the liability component are being amortized on a straight-line basis, which approximates the effective interest rate method, to interest expense over the term of the notes. The issuance costs attributable to the equity component are recorded as a reduction of the equity component within additional paid-in capital.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with generally accepted accounting principles in the United States (U.S. GAAP) requires management to make estimates, judgments, and assumptions that affect the reported amounts of assets and liabilities; the disclosure of contingent liabilities at the date of the financial statements; and the reported amounts of revenues and expenses during the reporting periods. Significant estimates, assumptions, and judgments are used for, but not limited to: revenue recognition, recoverability of accounts receivable, restructuring charges (credits), share-based compensation expense including estimated forfeitures, accounting for income taxes, useful lives assigned to long-lived assets for depreciation and amortization, impairment of goodwill and long-lived assets, the valuation of acquired intangible assets, the valuation of our convertible senior notes, and operating lease ROU assets and operating lease liabilities. We base our estimates on historical experience, knowledge of current business conditions, and various other factors we believe to be reasonable under the circumstances. These estimates are based on management’s knowledge about current events and expectations about actions we may undertake in the future. Actual results could differ from these estimates, and such differences could be material to our financial position and results of operations.
Recent Accounting Pronouncements	Recent Accounting Pronouncements Recently Issued Accounting Pronouncements Not Yet Adopted In August 2018, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) 2018-15, Intangibles—Goodwill and Other—Internal-Use Software (Subtopic 350-40): Customer's Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract. ASU 2018-15 aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with existing guidance contained within subtopic 350-40 to develop or obtain internal-use software. Early adoption is permitted and the guidance allows for a retrospective or prospective application. The guidance is effective for annual periods beginning after December 15, 2019, and we are currently in the process of evaluating the impact of this guidance. In July 2018, the FASB issued ASU 2018-09, Codification Improvements. ASU 2018-09 provides updates for technical corrections, clarifications, and other minor improvements to a wide variety of topics in the ASC. The transition method of adoption is dependent on the ASC topic impacted by this guidance. Additionally, some of the ASC topic updates are effective upon issuance of ASU 2018-09 and some of the ASC topic updates are effective at a future date. The ASC topic updates effective upon issuance of ASU 2018-09 do not impact our accounting for the respective ASC topics. For those ASC topic updates effective at a future date, we are currently in the process of evaluating the impact of this guidance update. Recently Adopted Accounting Pronouncements The FASB has issued four ASUs related to Accounting Standards Codification (ASC) 842. In March 2019, the FASB issued ASU 2019-01, Leases (Topic 842): Codification Improvements. In July 2018, the FASB issued ASU 2018-11, Leases (Topic 842): Targeted Improvements and ASU 2018-10, Codification Improvements to Topic 842, Leases. In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842). ASC 842 requires an entity to recognize a ROU asset and lease liability for all leases with terms of more than 12 months. Recognition, measurement, and presentation of expenses will depend on classification as a finance or operating lease. The amendments in this update also require certain quantitative and qualitative disclosures about leasing arrangements. We have adopted ASC 842 on January 1, 2019 and have elected the transition method of adoption that allows for a modified retrospective adoption with a cumulative-effect adjustment to the opening balance of accumulated deficit and recorded an immaterial decrease to our opening balance of accumulated deficit. As a result, we have not changed previously disclosed amounts or provided additional disclosures for comparative periods. We initially recorded ROU assets of $17.2 million and lease liabilities of $21.1 million on our condensed consolidated balance sheet. ASC 842 does not have a material impact to our condensed consolidated statement of operations. We have elected a package of transition practical expedients which include not reassessing whether any expired or existing contracts are or contain leases, not reassessing the lease classification of expired or existing leases, and not reassessing initial direct costs for existing leases. We have also elected a practical expedient to not separate lease and non-lease components. We did not elect the practical expedient to use hindsight in determining our lease terms or assessing impairment of our ROU assets. See Note 8. Leases for more information.
Revenue Recognition	Revenue Recognition Revenues are recognized when control of the promised goods or services is transferred to our customers, in an amount that reflects the consideration we expect to be entitled to in exchange for those goods or services. The majority of our revenues are recognized over time as services are performed, with certain revenues, most significantly the revenue share we earn from our print textbook partners, being recognized at the point in time when print textbooks are shipped to students.
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 stock options, warrants, restricted stock units (RSUs), performance-based restricted stock units (PSUs), and shares related to convertible senior notes, to the extent dilutive. Basic and diluted net loss per share was the same for each period presented as the inclusion of all potential common shares outstanding would have been anti-dilutive.

Revenues (Tables)

3 Months Ended

Mar. 31, 2019

Revenue from Contract with Customer [Abstract]

Disaggregation of Revenue

The following table sets forth our total net revenues for the periods shown disaggregated for our Chegg Services and Required Materials product lines (in thousands, except percentages):



	Three Months Ended March 31,				Change
	2019		2018		$		%
Chegg Services	$	75,292	$	56,277	$	19,015	34	%
Required Materials	22,117		20,672		1,445		7	%
Total net revenues	$	97,409	$	76,949	$	20,460	27	%

Schedule of Accounts Receivable

The following table presents our accounts receivable, net and deferred revenue balances (in thousands, except percentages):



					Change
	March 31, 2019		December 31, 2018		$			%
Accounts receivable, net	$	8,870	$	12,733	$	(3,863	)	(30	)%
Deferred revenue	$	26,276	$	17,418	$	8,858		51	%

Net Loss Per Share (Tables)

3 Months Ended

Mar. 31, 2019

Earnings Per Share [Abstract]

Schedule of Earnings Per Share, Basic and Diluted

The following table sets forth the computation of historical basic and diluted net loss per share (in thousands, except per share amounts):



	Three Months Ended March 31,
	2019			2018
Numerator:
Net loss	$	(4,318	)	$	(2,617	)
Denominator:
Weighted average shares used to compute net loss per share, basic and diluted	116,730			110,904

Net loss per share, basic and diluted	$	(0.04	)	$	(0.02	)

Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share

The following potential weighted-average shares of common stock outstanding were excluded from the computation of diluted net loss per share because including them would have been anti-dilutive (in thousands):



	Three Months Ended March 31,
	2019	2018
Options to purchase common stock	3,258	4,079
RSUs and PSUs	6,732	8,791
Shares related to convertible senior notes	3,332	—
Employee stock purchase plan	41	—
Total common stock equivalents	13,363	12,870

Cash and Cash Equivalents, and Investment (Tables)

3 Months Ended

Mar. 31, 2019

Cash and Cash Equivalents [Abstract]

Cash, Cash Equivalents and Investments

The following table shows our cash and cash equivalents, and investments’ adjusted cost, net unrealized gain/(loss) and fair value as of March 31, 2019 and December 31, 2018 (in thousands):



	March 31, 2019							December 31, 2018
	Cost		Net Unrealized Gain/(Loss)			Fair Value		Cost		Net Unrealized Loss			Fair Value
Cash and cash equivalents:
Cash	$	279,928	$	—		$	279,928	$	351,345	$	—		$	351,345
Money market funds	613,210		—			613,210		5,052		—			5,052
Commercial paper	21,369		(7		)	21,362		18,267		—			18,267
Total cash and cash equivalents	$	914,507	$	(7	)	$	914,500	$	374,664	$	—		$	374,664
Short-term investments:
Commercial paper	$	28,360	$	(3	)	$	28,357	$	40,500	$	(12	)	$	40,488
Corporate securities	26,235		(3		)	26,232		38,616		(87		)	38,529
U.S. treasury securities	15,488		3			15,491		14,333		(5		)	14,328
Total short-term investments	$	70,083	$	(3	)	$	70,080	$	93,449	$	(104	)	$	93,345
Long-term investments:
Corporate securities	$	10,842	$	56		$	10,898	$	14,429	$	(5	)	$	14,424
U.S. treasury securities	1,633		2			1,635		1,630		(2		)	1,628
Total long-term investments	$	12,475	$	58		$	12,533	$	16,059	$	(7	)	$	16,052

Schedule of Available-for-sale Securities Reconciliation

The adjusted cost and fair value of available-for-sale investments as of March 31, 2019 by contractual maturity were as follows (in thousands):



	Cost		Fair Value
Due in 1 year or less	$	91,452	$	91,442
Due in 1-2 years	12,475		12,533
Investments not due at a single maturity date	613,210		613,210
Total	$	717,137	$	717,185

Fair Value Measurement (Tables)

3 Months Ended

Mar. 31, 2019

Fair Value Disclosures [Abstract]

Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis

Financial instruments measured and recorded at fair value on a recurring basis as of March 31, 2019 and December 31, 2018 are classified based on the valuation technique level in the tables below (in thousands):



	March 31, 2019
	Total		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)
Assets:
Cash equivalents:
Money market funds	$	613,210	$	613,210	$	—
Commercial paper	21,362		—		21,362
Short-term investments:
Commercial paper	28,357		—		28,357
Corporate securities	26,232		—		26,232
U.S. treasury securities	15,491		15,491		—
Long-term investments:
Corporate securities	10,898		—		10,898
U.S. treasury securities	1,635		1,635		—
Total assets measured and recorded at fair value	$	717,185	$	630,336	$	86,849



	December 31, 2018
	Total		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)
Assets:
Cash equivalents:
Money market funds	$	5,052	$	5,052	$	—
Commercial paper	18,267		—		18,267
Short-term investments:	—
Commercial paper	40,488		—		40,488
Corporate securities	38,529		—		38,529
U.S. treasury securities	14,328		14,328		—
Long-term investments:
Corporate securities	14,424		—		14,424
U.S. treasury securities	1,628		1,628		—
Total assets measured and recorded at fair value	$	132,716	$	21,008	$	111,708

Fair Value Measurements, Nonrecurring

The carrying amounts and estimated fair values of the notes as of March 31, 2019 and December 31, 2018 are as follows (in thousands):



	March 31, 2019				December 31, 2018
	Carrying Amount		Estimated Fair Value		Carrying Amount		Estimated Fair Value
2025 notes	$	502,252	$	693,945	$	—	$	—
2023 notes	$	287,128	$	520,108	$	283,668	$	416,156
Convertible senior notes, net	$	789,380	$	1,214,053	$	283,668	$	416,156

Goodwill and Intangible Assets (Tables)

3 Months Ended

Mar. 31, 2019

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of Goodwill

Goodwill consists of the following (in thousands):



	March 31, 2019			December 31, 2018
Beginning balance	$	149,524		$	125,272
Additions due to acquisitions	—			24,673
Foreign currency translation adjustment	(43		)	(421		)
Ending balance	$	149,481		$	149,524

Finite-Lived Intangible Assets

Intangible assets as of March 31, 2019 and December 31, 2018 consist of the following (in thousands, except weighted-average amortization period):



	March 31, 2019
	Weighted-Average Amortization Period	Gross Carrying Amount			Accumulated Amortization			Net Carrying Amount
Developed technologies and content library	71	$	31,667		$	(14,821	)	$	16,846
Customer lists	47	9,970			(7,188		)	2,782
Trade names	44	6,113			(5,162		)	951
Non-compete agreements	31	2,018			(1,801		)	217
Indefinite-lived trade name	—	3,600			—			3,600
Foreign currency translation adjustment	—	(299		)	—			(299		)
Total intangible assets	61	$	53,069		$	(28,972	)	$	24,097



	December 31, 2018
	Weighted-Average Amortization Period	Gross Carrying Amount			Accumulated Amortization			Net Carrying Amount
Developed technologies and content library	71	$	31,667		$	(13,737	)	$	17,930
Customer lists	47	9,970			(6,847		)	3,123
Trade names	44	6,113			(4,863		)	1,250
Non-compete agreements	31	2,018			(1,735		)	283
Indefinite-lived trade name	—	3,600			—			3,600
Foreign currency translation adjustment	—	(271		)	—			(271		)
Total intangible assets	61	$	53,097		$	(27,182	)	$	25,915

Indefinite-lived Intangible Assets

Intangible assets as of March 31, 2019 and December 31, 2018 consist of the following (in thousands, except weighted-average amortization period):



	March 31, 2019
	Weighted-Average Amortization Period	Gross Carrying Amount			Accumulated Amortization			Net Carrying Amount
Developed technologies and content library	71	$	31,667		$	(14,821	)	$	16,846
Customer lists	47	9,970			(7,188		)	2,782
Trade names	44	6,113			(5,162		)	951
Non-compete agreements	31	2,018			(1,801		)	217
Indefinite-lived trade name	—	3,600			—			3,600
Foreign currency translation adjustment	—	(299		)	—			(299		)
Total intangible assets	61	$	53,069		$	(28,972	)	$	24,097



	December 31, 2018
	Weighted-Average Amortization Period	Gross Carrying Amount			Accumulated Amortization			Net Carrying Amount
Developed technologies and content library	71	$	31,667		$	(13,737	)	$	17,930
Customer lists	47	9,970			(6,847		)	3,123
Trade names	44	6,113			(4,863		)	1,250
Non-compete agreements	31	2,018			(1,735		)	283
Indefinite-lived trade name	—	3,600			—			3,600
Foreign currency translation adjustment	—	(271		)	—			(271		)
Total intangible assets	61	$	53,097		$	(27,182	)	$	25,915

Estimated Future Amortization Expense Related to Intangible Assets

As of March 31, 2019, the estimated future amortization expense related to our finite-lived intangible assets is as follows (in thousands):



Remaining nine months of 2019	$	4,658
2020	4,816
2021	3,423
2022	2,943
2023	2,276
Thereafter	2,381
Total	$	20,497

Convertible Senior Notes (Tables)

3 Months Ended

Mar. 31, 2019

Debt Disclosure [Abstract]

Schedule Of Net Proceeds From Debt Issuance

The total net proceeds from the notes are as follows (in thousands):



	2025 Notes			2023 Notes
Principal amount	$	700,000		$	345,000
Less initial purchasers’ discount	(16,625		)	(8,625		)
Less other issuance costs	(781		)	(757		)
Net proceeds	$	682,594		$	335,618

Schedule of Debt

The net carrying amount of the liability component of the notes is as follows (in thousands):



	March 31, 2019						December 31, 2018
	2025 Notes			2023 Notes			2023 Notes
Principal	$	700,000		$	345,000		$	345,000
Unamortized debt discount	(184,990		)	(51,725		)	(54,817		)
Unamortized issuance costs	(12,758		)	(6,147		)	(6,515		)
Net carrying amount	$	502,252		$	287,128		$	283,668

The net carrying amount of the equity component of the notes is as follows (in thousands):



	March 31, 2019						December 31, 2018
	2025 Notes			2023 Notes			2023 Notes
Debt discount for conversion option	$	185,500		$	64,193		$	64,193
Issuance costs	(4,613		)	(1,749		)	(1,749		)
Net carrying amount	$	180,887		$	62,444		$	62,444

Schedule Of Interest Expense Recognized

The following table sets forth the total interest expense recognized related to the notes (in thousands):



	Three Months Ended March 31, 2019
	2025 Notes		2023 Notes
Contractual interest expense	$	14	$	213
Amortization of debt discount	510		3,091
Amortization of issuance costs	35		369
Total interest expense	$	559	$	3,673

- Definition

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

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22)
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28541-108399

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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-Paragraph 1
-Subparagraph (SX 210.4-08.(e),(f))
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Reference 7: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 8: http://fasb.org/us-gaap/role/ref/legacyRef
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-Topic 942
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-Section 50
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-URI http://asc.fasb.org/extlink&oid=75038535&loc=d3e64711-112823

Reference 9: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
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-Section 55
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-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21475-112644

+ Details

Leases (Tables)

3 Months Ended

Mar. 31, 2019

Leases [Abstract]

Lessee, Operating Lease, Liability, Maturity

The aggregate future minimum lease payments and reconciliation to lease liabilities as of March 31, 2019, are as follows (in thousands):



	March 31, 2019
Remaining nine months of 2019	$	4,101
2020	5,200
2021	4,724
2022	3,948
2023	3,424
Thereafter	788
Total future minimum lease payments	22,185
Less imputed interest	(2,121		)
Total lease liabilities	$	20,064

The aggregate future minimum lease payments as of December 31, 2018, are as follows (in thousands):



	December 31, 2018
2019	$	5,222
2020	5,251
2021	4,775
2022	3,999
2023	3,421
Thereafter	788
Total	$	23,456

Stockholders' Equity (Tables)

3 Months Ended

Mar. 31, 2019

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Stock-Based Compensation Expense for Employees and Non-Employees

Total share-based compensation expense recorded for employees and non-employees, is as follows (in thousands):



	Three Months Ended March 31,
	2019		2018
Cost of revenues	$	125	$	94
Research and development	4,917		4,133
Sales and marketing	1,808		1,589
General and administrative	8,188		5,826
Total share-based compensation expense	$	15,038	$	11,642

Summary of Restricted Stock Unit Activity

Activity for RSUs and PSUs is as follows:



	RSUs and PSUs Outstanding
	Number of RSUs and PSUs Outstanding		Weighted Average Grant Date Fair Value
Balance at December 31, 2018	10,804,808		$	11.87
Granted	1,440,428		39.95
Released	(4,352,468	)	8.97
Canceled	(727,939	)	7.12
Balance at March 31, 2019	7,164,829		$	19.76

Restructuring Charges (Tables)

3 Months Ended

Mar. 31, 2019

Restructuring and Related Activities [Abstract]

Schedule of Restructuring Reserve by Type of Cost

The following table summarizes the activity related to the accrual for restructuring charges (in thousands):



	2017 Restructuring Plan						2015 Restructuring Plan
	Workforce Reduction Costs			Lease Termination and Other Costs			Lease Termination and Other Costs			Total
Balance at January 1, 2018	$	44		$	—		$	221		$	265
Restructuring charges	253			19			317			589
Cash payments	(151		)	(19		)	(218		)	(388		)
Write-offs	—			—			(18		)	(18		)
Balance at December 31, 2018	146			—			302			448
Cumulative-effect adjustment to accumulated deficit related to adoption of ASU 2016-02	—			—			(302		)	(302		)
Restructuring charges	22			—			—			22
Cash payments	(132		)	—			—			(132		)
Balance at March 31, 2019	$	36		$	—		$	—		$	36

Background and Basis of Presentation (Details) - USD ($)	Mar. 31, 2019	Jan. 01, 2019	Dec. 31, 2018	Apr. 30, 2018
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Right of use assets	$ 15,875,000		$ 0
Operating lease liability	20,064,000
Senior Notes \| 0.125% Convertible Senior Notes Due 2025
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Face value	$ 700,000,000
Interest rate, stated percentage	0.125%
Senior Notes \| 0.25% Convertible Senior Notes Due 2023
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Face value	$ 345,000,000		$ 345,000,000	$ 345,000,000
Interest rate, stated percentage				0.25%
Accounting Standards Update 2016-02
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Right of use assets		$ 17,200,000
Operating lease liability		$ 21,100,000

Revenues (Details) - USD ($) $ in Thousands	3 Months Ended
Revenues (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Total net revenues	$ 97,409	$ 76,949
Change in total net revenues	$ 20,460
Change in total net revenues, percent	27.00%
Contract with customer, liability, revenue recognized	$ 12,400
Aggregate amount of unsatisfied performance obligations	29,000
Accounts receivable, net	8,870		$ 12,733
Change in accounts receivable	$ (3,863)
Change in accounts receivable, percent	(30.00%)
Deferred revenue	$ 26,276		$ 17,418
Change in deferred revenue	$ 8,858
Change in deferred revenue, percent	51.00%
Chegg Services
Disaggregation of Revenue [Line Items]
Total net revenues	$ 75,292	56,277
Change in total net revenues	$ 19,015
Change in total net revenues, percent	34.00%
Required Materials
Disaggregation of Revenue [Line Items]
Total net revenues	$ 22,117	$ 20,672
Change in total net revenues	$ 1,445
Change in total net revenues, percent	7.00%

Net Loss Per Share - Computation of Basic and Diluted Net Loss Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Numerator:
Net loss	$ (4,318)	$ (2,617)
Denominator:
Weighted average shares used to compute net loss per share, basic and diluted (in shares)	116,730	110,904
Net loss per share, basic and diluted (in dollars per share)	$ (0.04)	$ (0.02)

- Definition

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

+ References + Details

Net Loss Per Share - Shares Excluded From Computation Of Diluted Net Loss Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Apr. 30, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total common stock equivalents (in shares)	13,363	12,870
Options to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total common stock equivalents (in shares)	3,258	4,079
RSUs and PSUs
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total common stock equivalents (in shares)	6,732	8,791
Shares related to convertible senior notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total common stock equivalents (in shares)	3,332	0
Employee stock purchase plan
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total common stock equivalents (in shares)	41	0
0.25% Convertible Senior Notes Due 2023 \| Shares related to convertible senior notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Face value	$ 345,000,000		$ 345,000,000	$ 345,000,000
Conversion price				$ 26.95
Interest rate, stated percentage				0.25%
0.125% Convertible Senior Notes Due 2025 \| Shares related to convertible senior notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Face value	$ 700,000,000
Conversion price	$ 51.56
Interest rate, stated percentage	0.125%
Capped Call \| 0.25% Convertible Senior Notes Due 2023 \| Shares related to convertible senior notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Conversion price	$ 40.68
Capped Call \| 0.125% Convertible Senior Notes Due 2025 \| Shares related to convertible senior notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Conversion price	$ 79.32

Cash and Cash Equivalents, and Investment - Additional Information (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018	Oct. 31, 2018
Schedule of Investments [Line Items]
Restricted cash	$ 1.0	$ 1.3
Cost method investment			$ 10.0
Other Assets \| Equity Investments
Schedule of Investments [Line Items]
Investments	$ 3.0

Cash and Cash Equivalents, and Investment - Schedule of Available For Sale Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Cost	$ 717,137
Fair Value	717,185
Cash and cash equivalents:
Debt Securities, Available-for-sale [Line Items]
Cost	914,507	$ 374,664
Net Unrealized Gain/(Loss)	(7)	0
Fair Value	914,500	374,664
Short-term investments:
Debt Securities, Available-for-sale [Line Items]
Cost	70,083	93,449
Net Unrealized Gain/(Loss)	(3)	(104)
Fair Value	70,080	93,345
Total long-term investments
Debt Securities, Available-for-sale [Line Items]
Cost	12,475	16,059
Net Unrealized Gain/(Loss)	58	(7)
Fair Value	12,533	16,052
Corporate securities \| Short-term investments:
Debt Securities, Available-for-sale [Line Items]
Cost	26,235	38,616
Net Unrealized Gain/(Loss)	(3)	(87)
Fair Value	26,232	38,529
Corporate securities \| Total long-term investments
Debt Securities, Available-for-sale [Line Items]
Cost	10,842	14,429
Net Unrealized Gain/(Loss)	56	(5)
Fair Value	10,898	14,424
Commercial paper \| Short-term investments:
Debt Securities, Available-for-sale [Line Items]
Cost	28,360	40,500
Net Unrealized Gain/(Loss)	(3)	(12)
Fair Value	28,357	40,488
U.S. treasury securities \| Short-term investments:
Debt Securities, Available-for-sale [Line Items]
Cost	15,488	14,333
Net Unrealized Gain/(Loss)	3	(5)
Fair Value	15,491	14,328
U.S. treasury securities \| Total long-term investments
Debt Securities, Available-for-sale [Line Items]
Cost	1,633	1,630
Net Unrealized Gain/(Loss)	2	(2)
Fair Value	1,635	1,628
Cash \| Cash and cash equivalents:
Debt Securities, Available-for-sale [Line Items]
Cost	279,928	351,345
Net Unrealized Gain/(Loss)	0	0
Fair Value	279,928	351,345
Money market funds \| Cash and cash equivalents:
Debt Securities, Available-for-sale [Line Items]
Cost	613,210	5,052
Net Unrealized Gain/(Loss)	0	0
Fair Value	613,210	5,052
Commercial paper \| Cash and cash equivalents:
Debt Securities, Available-for-sale [Line Items]
Cost	21,369	18,267
Net Unrealized Gain/(Loss)	(7)	0
Fair Value	$ 21,362	$ 18,267

Cash and Cash Equivalents, and Investment - Contractual Maturity (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019 USD ($)
Cash and Cash Equivalents [Abstract]
Due in 1 year or less, Cost	$ 91,452
Due in 1-2 years, Cost	12,475
Investments not due at a single maturity date, Cost	613,210
Cost	717,137
Due in 1 year or less, Fair Value	91,442
Due in 1-2 years, Fair Value	12,533
Investments not due at a single maturity date, Fair Value	613,210
Total, Fair Value	$ 717,185
Weighted average maturity	1 month

Fair Value Measurement - Financial Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	$ 70,080	$ 93,345
Long-term investments	12,533	16,052
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured and recorded at fair value	717,185	132,716
Fair Value, Measurements, Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured and recorded at fair value	630,336	21,008
Fair Value, Measurements, Recurring \| Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets measured and recorded at fair value	86,849	111,708
Commercial paper \| Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	28,357	40,488
Commercial paper \| Fair Value, Measurements, Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	0	0
Commercial paper \| Fair Value, Measurements, Recurring \| Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	28,357	40,488
Corporate securities \| Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	26,232	38,529
Long-term investments	10,898	14,424
Corporate securities \| Fair Value, Measurements, Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	0	0
Long-term investments	0	0
Corporate securities \| Fair Value, Measurements, Recurring \| Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	26,232	38,529
Long-term investments	10,898	14,424
U.S. treasury securities \| Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	15,491	14,328
Long-term investments	1,635	1,628
U.S. treasury securities \| Fair Value, Measurements, Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	15,491	14,328
Long-term investments	1,635	1,628
U.S. treasury securities \| Fair Value, Measurements, Recurring \| Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	0	0
Long-term investments	0	0
Money market funds \| Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	613,210	5,052
Money market funds \| Fair Value, Measurements, Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	613,210	5,052
Money market funds \| Fair Value, Measurements, Recurring \| Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Commercial paper \| Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	21,362	18,267
Commercial paper \| Fair Value, Measurements, Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Commercial paper \| Fair Value, Measurements, Recurring \| Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	$ 21,362	$ 18,267

Fair Value Measurement - Debt (Details) - Senior Notes - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Carrying Amount \| Fair Value, Measurements, Nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Convertible senior notes	$ 789,380	$ 283,668
Estimated Fair Value \| Fair Value, Measurements, Nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Convertible senior notes	1,214,053	416,156
0.125% Convertible Senior Notes Due 2025
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unamortized debt discount	184,990
Unamortized issuance costs	12,758
0.125% Convertible Senior Notes Due 2025 \| Carrying Amount \| Fair Value, Measurements, Nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Convertible senior notes	502,252	0
0.125% Convertible Senior Notes Due 2025 \| Estimated Fair Value \| Fair Value, Measurements, Nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Convertible senior notes	693,945	0
0.25% Convertible Senior Notes Due 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unamortized debt discount	51,725	54,817
Unamortized issuance costs	6,147	6,515
0.25% Convertible Senior Notes Due 2023 \| Carrying Amount \| Fair Value, Measurements, Nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Convertible senior notes	287,128	283,668
0.25% Convertible Senior Notes Due 2023 \| Estimated Fair Value \| Fair Value, Measurements, Nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Convertible senior notes	$ 520,108	$ 416,156

Goodwill and Intangible Assets - Goodwill (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Goodwill [Roll Forward]
Beginning balance	$ 149,524	$ 125,272
Additions due to acquisitions	0	24,673
Foreign currency translation adjustment	(43)	(421)
Ending balance	$ 149,481	$ 149,524

Goodwill and Intangible Assets - Finite-lived and Indefinite-lived Intangibe Assets (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Finite Lived Intangible Assets [Line Items]
Weighted-Average Amortization Period	61 months	61 months
Accumulated Amortization	$ (28,972)	$ (27,182)
Net Carrying Amount	20,497
Indefinite-lived trade name	3,600	3,600
Foreign currency translation adjustment	(299)	(271)
Total intangible assets, gross carrying amount	53,069	53,097
Intangible assets, net	$ 24,097	$ 25,915
Developed technologies and content library
Finite Lived Intangible Assets [Line Items]
Weighted-Average Amortization Period	71 months	71 months
Gross Carrying Amount	$ 31,667	$ 31,667
Accumulated Amortization	(14,821)	(13,737)
Net Carrying Amount	$ 16,846	$ 17,930
Customer lists
Finite Lived Intangible Assets [Line Items]
Weighted-Average Amortization Period	47 months	47 months
Gross Carrying Amount	$ 9,970	$ 9,970
Accumulated Amortization	(7,188)	(6,847)
Net Carrying Amount	$ 2,782	$ 3,123
Trade names
Finite Lived Intangible Assets [Line Items]
Weighted-Average Amortization Period	44 months	44 months
Gross Carrying Amount	$ 6,113	$ 6,113
Accumulated Amortization	(5,162)	(4,863)
Net Carrying Amount	$ 951	$ 1,250
Non-compete agreements
Finite Lived Intangible Assets [Line Items]
Weighted-Average Amortization Period	31 months	31 months
Gross Carrying Amount	$ 2,018	$ 2,018
Accumulated Amortization	(1,801)	(1,735)
Net Carrying Amount	$ 217	$ 283

Goodwill and Intangible Assets - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Acquisition-Related Intangible Assets
Finite Lived Intangible Assets [Line Items]
Amortization expense of acquisition related to acquired intangible assets	$ 1.8	$ 1.4

Goodwill and Intangible Assets - Estimated Future Amortization Expense Related to Intangible Assets (Details) $ in Thousands	Mar. 31, 2019 USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
Remaining nine months of 2019	$ 4,658
2020	4,816
2021	3,423
2022	2,943
2023	2,276
Thereafter	2,381
Net Carrying Amount	$ 20,497

Convertible Senior Notes - Convertible Senior Notes (Details)		1 Months Ended		3 Months Ended
	Jun. 30, 2018 USD ($)	Mar. 31, 2019 USD ($) $ / shares shares	Apr. 30, 2018 USD ($) day $ / shares shares	Mar. 31, 2019 USD ($) $ / shares	Mar. 31, 2018 USD ($)	Dec. 31, 2018 USD ($)
Debt Instrument [Line Items]
Net proceeds				$ 682,594,000	$ 0
Senior Notes \| 0.125% Convertible Senior Notes Due 2025
Debt Instrument [Line Items]
Face value		$ 700,000,000		$ 700,000,000
Interest rate, stated percentage		0.125%		0.125%
Less initial purchasers’ discount		$ (16,625,000)
Less other issuance costs		(781,000)
Net proceeds		$ 682,594,000
Conversion price \| $ / shares		$ 51.56		$ 51.56
Equity component		$ 180,887,000		$ 180,887,000
Debt issuance costs		(17,400,000)		$ (17,400,000)
Debt instrument, remaining useful life				6 years
Debt conversion, converted instrument, amount	$ 517,600,000
Debt instrument, if-converted value less than principal		$ (182,400,000)
Interest rate, effective percentage		5.40%		5.40%
Senior Notes \| 0.25% Convertible Senior Notes Due 2023
Debt Instrument [Line Items]
Face value		$ 345,000,000	$ 345,000,000	$ 345,000,000		$ 345,000,000
Interest rate, stated percentage			0.25%
Option to purchase additional notes			$ 45,000,000
Less initial purchasers’ discount			(8,625,000)
Less other issuance costs			(757,000)
Net proceeds			$ 335,618,000
Conversion ratio		0.0193956	0.0371051
Conversion price \| $ / shares			$ 26.95
Equity component		$ 62,444,000	$ 64,200,000	$ 62,444,000		$ 62,444,000
Debt issuance costs			(9,400,000)
Debt instrument, remaining useful life				4 years 1 month
Share price (in dollars per share) \| $ / shares		$ 38.12		$ 38.12
Debt conversion, converted instrument, amount	$ 488,000,000
Debt instrument, if-converted value in excess of principal			$ 143,000,000
Interest rate, effective percentage			4.34%
Sale Price Is Greater Or Equal 130% \| Senior Notes \| 0.25% Convertible Senior Notes Due 2023
Debt Instrument [Line Items]
Threshold trading days \| day			20
Threshold consecutive trading days \| day			30
Threshold percentage of stock price trigger			130.00%
Trading Price Per $1,000 Principal Amount Less Than 98% \| Senior Notes \| 0.25% Convertible Senior Notes Due 2023
Debt Instrument [Line Items]
Threshold trading days \| day			5
Threshold consecutive trading days \| day			10
Trading Price Per $1,000 Principal Amount Less Than 98% \| Senior Notes \| 0.25% Convertible Senior Notes Due 2023 \| Maximum
Debt Instrument [Line Items]
Threshold percentage of stock price trigger			98.00%
Liability component \| Senior Notes \| 0.125% Convertible Senior Notes Due 2025
Debt Instrument [Line Items]
Net carrying amount		$ 514,500,000		$ 514,500,000
Equity component		185,500,000		185,500,000
Debt issuance costs		(12,800,000)		(12,800,000)
Liability component \| Senior Notes \| 0.25% Convertible Senior Notes Due 2023
Debt Instrument [Line Items]
Net carrying amount			$ 280,800,000
Debt issuance costs			(7,600,000)
Equity component \| Senior Notes \| 0.125% Convertible Senior Notes Due 2025
Debt Instrument [Line Items]
Debt issuance costs		(4,600,000)		$ (4,600,000)
Equity component \| Senior Notes \| 0.25% Convertible Senior Notes Due 2023
Debt Instrument [Line Items]
Debt issuance costs			(1,700,000)
Capped Call \| Senior Notes \| 0.125% Convertible Senior Notes Due 2025
Debt Instrument [Line Items]
Net proceeds		$ 85,100,000
Conversion price \| $ / shares		$ 79.32		$ 79.32
Shares covered by capped call transactions (in shares) \| shares		13,576,920
Capped Call \| Senior Notes \| 0.25% Convertible Senior Notes Due 2023
Debt Instrument [Line Items]
Net proceeds			$ 39,200,000
Conversion price \| $ / shares		$ 40.68		$ 40.68
Shares covered by capped call transactions (in shares) \| shares			12,801,260

Convertible Senior Notes - Net Carrying Amount (Details) - Senior Notes - USD ($)	Mar. 31, 2019	Dec. 31, 2018	Apr. 30, 2018
0.125% Convertible Senior Notes Due 2025
Debt Instrument [Line Items]
Principal	$ 700,000,000
Unamortized debt discount	(184,990,000)
Unamortized issuance costs	(12,758,000)
Debt discount for conversion option	185,500,000
Issuance costs	(4,613,000)
Net carrying amount	180,887,000
0.25% Convertible Senior Notes Due 2023
Debt Instrument [Line Items]
Principal	345,000,000	$ 345,000,000	$ 345,000,000
Unamortized debt discount	(51,725,000)	(54,817,000)
Unamortized issuance costs	(6,147,000)	(6,515,000)
Debt discount for conversion option	64,193,000	64,193,000
Issuance costs	(1,749,000)	(1,749,000)
Net carrying amount	62,444,000	62,444,000	$ 64,200,000
Carrying Amount \| Fair Value, Measurements, Nonrecurring
Debt Instrument [Line Items]
Net carrying amount	789,380,000	283,668,000
Carrying Amount \| Fair Value, Measurements, Nonrecurring \| 0.125% Convertible Senior Notes Due 2025
Debt Instrument [Line Items]
Net carrying amount	502,252,000	0
Carrying Amount \| Fair Value, Measurements, Nonrecurring \| 0.25% Convertible Senior Notes Due 2023
Debt Instrument [Line Items]
Net carrying amount	$ 287,128,000	$ 283,668,000

Convertible Senior Notes - Interest Expense Recognized (Details) - Senior Notes - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
0.125% Convertible Senior Notes Due 2025
Debt Instrument [Line Items]
Contractual interest expense	$ 14
Amortization of debt discount	510
Amortization of issuance costs	35
Total interest expense	$ 559
0.25% Convertible Senior Notes Due 2023
Debt Instrument [Line Items]
Contractual interest expense		$ 213
Amortization of debt discount		3,091
Amortization of issuance costs		369
Total interest expense		$ 3,673

Leases - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Leases [Abstract]
Right of use assets	$ 15,875	$ 0
Operating lease liability	$ 20,064
Weighted average remaining lease term for operating lease	4 years 3 months 11 days
Weighted average discount rate used to determine the operating lease liability	4.70%
Operating lease expense, net of accretion	$ 1,300

Leases - Maturities of Operating Lease Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Leases [Abstract]
Remaining nine months of 2019	$ 4,101
2020	5,200
2021	4,724
2022	3,948
2023	3,424
2024	788
Total future minimum lease payments	22,185
Less imputed interest	(2,121)
Total lease liabilities	$ 20,064
2019		$ 5,222
2020		5,251
2021		4,775
2022		3,999
2023		3,421
Thereafter		788
Total		$ 23,456

Stockholders' Equity - Share-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Share-based compensation expense	$ 15,038	$ 11,642
Cost of revenues
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Share-based compensation expense	125	94
Research and development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Share-based compensation expense	4,917	4,133
Sales and marketing
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Share-based compensation expense	1,808	1,589
General and administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Share-based compensation expense	$ 8,188	$ 5,826

Stockholders' Equity - Additional Information (Details) $ / shares in Units, $ in Millions	1 Months Ended	3 Months Ended
	Mar. 31, 2019 USD ($) $ / shares shares	Mar. 31, 2019 USD ($) $ / shares
RSUs and PSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation costs related to restricted stock units \| $	$ 98.1	$ 98.1
Weighted average vesting period for recognition of compensation expense		1 year 10 months 21 days
Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares repurchased (in shares) \| shares	504,286
Share price (in dollars per share) \| $ / shares	$ 39.66	$ 39.66

Stockholders' Equity - Summary of Restricted Stock Unit Activity (Details) - RSUs and PSUs	3 Months Ended
	Mar. 31, 2019 $ / shares shares
Number of RSUs and PSUs Outstanding
Number of RSUs and PSUs Outstanding, Beginning (shares) \| shares	10,804,808
Number of RSUs and PSUs, Granted (shares) \| shares	1,440,428
Number of RSUs and PSUs, Released (shares) \| shares	(4,352,468)
Number of RSUs and PSUs, Canceled (shares) \| shares	(727,939)
Number of RSUs and PSUs Outstanding, Ending (shares) \| shares	7,164,829
Weighted Average Grant Date Fair Value
Weighted Average Grant Date Fair Value, Beginning balance (in dollars per share) \| $ / shares	$ 11.87
Weighted Average Grant Date Fair Value, Granted (in dollars per share) \| $ / shares	39.95
Weighted Average Grant Date Fair Value, Released (in dollars per share) \| $ / shares	8.97
Weighted Average Grant Date Fair Value, Canceled (in dollars per share) \| $ / shares	7.12
Weighted Average Grant Date Fair Value, Ending balance (in dollars per share) \| $ / shares	$ 19.76

Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended
Income Taxes (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Mar. 31, 2018
Income Tax Disclosure [Abstract]
Provision for income taxes	$ 626	$ 541

Restructuring Charges - Narrative (Details)	3 Months Ended
Restructuring Charges - Narrative (Details)	Mar. 31, 2019 position
2017 Restructuring Plan \| Workforce Reduction Costs
Restructuring Cost and Reserve [Line Items]
Number of positions eliminated	55

Restructuring Charges - Restructuring Reserve (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Restructuring Reserve [Roll Forward]
Beginning balance	$ 448	$ 265	$ 265
Restructuring charges	22	220	589
Cash payments	(132)		(388)
Write-offs			(18)
Ending balance	36		448
2017 Restructuring Plan \| Workforce Reduction Costs
Restructuring Reserve [Roll Forward]
Beginning balance	146	44	44
Restructuring charges	22		253
Cash payments	(132)		(151)
Write-offs			0
Ending balance	36		146
2017 Restructuring Plan \| Lease Termination and Other Costs
Restructuring Reserve [Roll Forward]
Beginning balance	0	0	0
Restructuring charges	0		19
Cash payments	0		(19)
Write-offs			0
Ending balance	0		0
2015 Restructuring Plan \| Lease Termination and Other Costs
Restructuring Reserve [Roll Forward]
Beginning balance	302	$ 221	221
Restructuring charges	0		317
Cash payments	0		(218)
Write-offs			(18)
Ending balance	0		$ 302
Accounting Standards Update 2016-02
Restructuring Reserve [Roll Forward]
Write-offs	(302)
Accounting Standards Update 2016-02 \| 2017 Restructuring Plan \| Workforce Reduction Costs
Restructuring Reserve [Roll Forward]
Write-offs	0
Accounting Standards Update 2016-02 \| 2017 Restructuring Plan \| Lease Termination and Other Costs
Restructuring Reserve [Roll Forward]
Write-offs	0
Accounting Standards Update 2016-02 \| 2015 Restructuring Plan \| Lease Termination and Other Costs
Restructuring Reserve [Roll Forward]
Write-offs	$ (302)

Related-Party Transactions (Details)	3 Months Ended
Related-Party Transactions (Details)	Mar. 31, 2019 USD ($) board_member	Mar. 31, 2018 USD ($)	Dec. 31, 2018 USD ($)
Adobe Systems \| Chief Executive Officer
Related Party Transaction [Line Items]
Purchases from related party	$ 1,000,000	$ 1,700,000
Revenue from related parties	0	100,000
Receivables from related party	0		$ 0
Cengage \| Chief Executive Officer
Related Party Transaction [Line Items]
Revenue from related parties	1,200,000	1,900,000
Due to related parties	500,000		$ 100,000
Cengage \| Board Of Directors Member
Related Party Transaction [Line Items]
Purchases from related party	$ 9,100,000	5,100,000
Number of board members appointed to Board of Directors of related party \| board_member	1
PayPal \| Board Of Directors Member
Related Party Transaction [Line Items]
Expenses from transactions with related party	$ 400,000	$ 400,000
Synack, Inc. \| Board Of Directors Member
Related Party Transaction [Line Items]
Purchases from related party	$ 300,000
Number of board members appointed to Board of Directors of related party \| board_member	1

Subsequent Event (Details) - 0.125% Convertible Senior Notes Due 2025 - Senior Notes - Subsequent Event	Apr. 03, 2019 USD ($)
Subsequent Event [Line Items]
Face value	$ 100,000,000
Payments for additional privately negotiated capped call transactions	$ 12,200,000

Label	Element	Value
Accounting Standards Update 2018-02 And 2014-09 [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ (77,000)
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	(111,000)
Accounting Standards Update 2018-02 And 2014-09 [Member] \| Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	(77,000)
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ (111,000)