Chegg (CHGG) 10-Q 29 Jul 19 2019 Q2 Quarterly report Financial data

Cover Page

Cover Page - shares	6 Months Ended
	Jun. 30, 2019	Jul. 26, 2019
Cover page.
Entity Address, Address Line One	3990 Freedom Circle
Entity Address, City or Town	Santa Clara
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	95054
City Area Code	408
Local Phone Number	855-5700
Entity Incorporation, State or Country Code	DE
Title of 12(b) Security	Common stock, $0.001 par value per share
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Shell Company	false
Entity File Number	001-36180
Document Transition Report	false
Document Quarterly Report	true
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	Jun. 30, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q2
Amendment Flag	false
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Common Stock, Shares Outstanding		119,651,393
Trading Symbol	CHGG
Security Exchange Name	NYSE
Entity Tax Identification Number	20-3237489

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Current assets
Cash and cash equivalents	$ 555,792	$ 374,664
Short-term investments	259,399	93,345
Accounts receivable, net of allowance for doubtful accounts of $23 and $229 at June 30, 2019 and December 31, 2018, respectively	5,948	12,733
Prepaid expenses	12,152	4,673
Other current assets	14,608	9,510
Total current assets	847,899	494,925
Long-term investments	288,682	16,052
Property and equipment, net	76,962	59,904
Goodwill	149,466	149,524
Intangible assets, net	22,374	25,915
Right of use assets	14,756	0
Other assets	15,544	14,618
Total assets	1,415,683	760,938
Current liabilities
Accounts payable	3,131	8,177
Deferred revenue	18,821	17,418
Current operating lease liabilities	4,774	0
Accrued liabilities	37,425	34,077
Total current liabilities	64,151	59,672
Long-term liabilities
Convertible senior notes, net	874,126	283,668
Long-term operating lease liabilities	14,243	0
Other long-term liabilities	3,592	6,964
Total long-term liabilities	891,961	290,632
Total liabilities	956,112	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; 119,335,960 and 115,500,418 shares issued and outstanding at June 30, 2019 and December 31, 2018, respectively	119	116
Additional paid-in capital	873,104	818,113
Accumulated other comprehensive loss	(618)	(1,019)
Accumulated deficit	(413,034)	(406,576)
Total stockholders' equity	459,571	410,634
Total liabilities and stockholders' equity	$ 1,415,683	$ 760,938

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Allowance for doubtful accounts receivable, current	$ 23	$ 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	119,335,960	115,500,418
Common stock, shares outstanding	119,335,960	115,500,418

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Income Statement [Abstract]
Net revenues	$ 93,862	$ 74,222	$ 191,271	$ 151,171
Cost of revenues	20,518	17,784	43,853	38,008
Gross profit	73,344	56,438	147,418	113,163
Operating expenses:
Research and development	32,065	26,218	64,757	51,751
Sales and marketing	11,795	11,437	30,512	26,773
General and administrative	22,622	19,479	46,292	37,735
Restructuring charges	47	15	69	235
Total operating expenses	66,529	57,149	141,630	116,494
Income (loss) from operations	6,815	(711)	5,788	(3,331)
Interest expense and other income, net:
Interest expense, net	(13,514)	(3,664)	(17,746)	(3,684)
Other income, net	5,253	894	6,820	1,458
Total interest expense and other income, net	(8,261)	(2,770)	(10,926)	(2,226)
Loss before provision for income taxes	(1,446)	(3,481)	(5,138)	(5,557)
Provision for income taxes	583	428	1,209	969
Net loss	$ (2,029)	$ (3,909)	$ (6,347)	$ (6,526)
Net loss per share, basic and diluted (in dollars per share)	$ (0.02)	$ (0.03)	$ (0.05)	$ (0.06)
Weighted average shares used to compute net loss per share, basic and diluted (in shares)	118,790	112,738	117,766	111,826

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Statement of Comprehensive Income [Abstract]
Net loss	$ (2,029)	$ (3,909)	$ (6,347)	$ (6,526)
Other comprehensive income:
Change in net unrealized gain (loss) on available for sale investments, net of tax	333	114	452	23
Change in foreign currency translation adjustments, net of tax	(51)	(913)	(51)	(402)
Other comprehensive income (loss)	282	(799)	401	(379)
Total comprehensive loss	$ (1,747)	$ (4,708)	$ (5,946)	$ (6,905)

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Unaudited) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (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]
Equity component of convertible senior notes, net of issuance costs	62,444		62,444
Purchase of convertible senior notes capped call	(39,227)		(39,227)
Repurchase of common stock (in shares)		(983,000)
Repurchase of common stock	(20,000)	$ (1)	(19,999)
Issuance of common stock upon exercise of stock options and ESPP (in shares)		2,034,000
Issuance of common stock upon exercise of stock options and ESPP	18,048	$ 2	18,046
Net issuance of common stock for settlement of RSUs (in shares)		2,798,000
Net issuance of common stock for settlement of RSUs	(40,311)	$ 3	(40,314)
Warrant exercises (in shares)		34,000
Warrant exercises	0		0
Share-based compensation expense	23,685		23,685
Other comprehensive income (loss)	(379)			(379)
Net loss	(6,526)				(6,526)
Beginning balance at Jun. 30, 2018	388,719	$ 114	787,480	(661)	(398,214)
Common stock, ending balance (in shares) at Jun. 30, 2018		113,551,000
Common stock, beginning balance (in shares) at Mar. 31, 2018		112,749,000
Beginning balance at Mar. 31, 2018	370,011	$ 113	764,065	138	(394,305)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Equity component of convertible senior notes, net of issuance costs	62,444		62,444
Purchase of convertible senior notes capped call	(39,227)		(39,227)
Repurchase of common stock (in shares)		(983,000)
Repurchase of common stock	(20,000)	$ (1)	(19,999)
Issuance of common stock upon exercise of stock options and ESPP (in shares)		1,406,000
Issuance of common stock upon exercise of stock options and ESPP	12,830	$ 2	12,828
Net issuance of common stock for settlement of RSUs (in shares)		379,000
Net issuance of common stock for settlement of RSUs	(4,674)	$ 0	(4,674)
Share-based compensation expense	12,043		12,043
Other comprehensive income (loss)	(799)			(799)
Net loss	(3,909)				(3,909)
Beginning balance at Jun. 30, 2018	$ 388,719	$ 114	787,480	(661)	(398,214)
Common stock, ending balance (in shares) at Jun. 30, 2018		113,551,000
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	206,747		206,747
Purchase of convertible senior notes capped call	(97,200)		(97,200)
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)		1,554,000
Issuance of common stock upon exercise of stock options and ESPP	16,046	$ 2	16,044
Net issuance of common stock for settlement of RSUs (in shares)		2,745,000
Net issuance of common stock for settlement of RSUs	(82,249)	$ 2	(82,251)
Issuance of common stock in connection with acquisition (in shares)		41,000
Issuance of common stock in connection with acquisition	1,160		1,160
Share-based compensation expense	30,490		30,490
Other comprehensive income (loss)	401			401
Net loss	(6,347)				(6,347)
Beginning balance at Jun. 30, 2019	$ 459,571	$ 119	873,104	(618)	(413,034)
Common stock, ending balance (in shares) at Jun. 30, 2019	119,335,960	119,336,000
Common stock, beginning balance (in shares) at Mar. 31, 2019		118,197,000
Beginning balance at Mar. 31, 2019	$ 428,137	$ 118	839,924	(900)	(411,005)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Equity component of convertible senior notes, net of issuance costs	25,860		25,860
Purchase of convertible senior notes capped call	(12,150)		(12,150)
Issuance of common stock upon exercise of stock options and ESPP (in shares)		845,000
Issuance of common stock upon exercise of stock options and ESPP	10,226	$ 1	10,225
Net issuance of common stock for settlement of RSUs (in shares)		294,000
Net issuance of common stock for settlement of RSUs	(6,207)	$ 0	(6,207)
Share-based compensation expense	15,452		15,452
Other comprehensive income (loss)	282			282
Net loss	(2,029)				(2,029)
Beginning balance at Jun. 30, 2019	$ 459,571	$ 119	$ 873,104	$ (618)	$ (413,034)
Common stock, ending balance (in shares) at Jun. 30, 2019	119,335,960	119,336,000

CONDENSED CONSOLIDATED STATEM_4

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Cash flows from operating activities
Net loss	$ (6,347)	$ (6,526)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization expense	13,934	10,665
Share-based compensation expense	30,490	23,685
Amortization of debt discount and issuance costs	17,025	3,421
Deferred income taxes	39	(315)
Operating lease expense, net of accretion	2,168	0
Other non-cash items	(115)	115
Change in assets and liabilities:
Accounts receivable	6,944	2,609
Prepaid expenses and other current assets	(12,942)	(6,773)
Other assets	2,334	(500)
Accounts payable	(5,417)	(1,712)
Deferred revenue	1,403	270
Accrued liabilities	2,397	(2,678)
Other liabilities	(4,067)	1,254
Net cash provided by operating activities	47,846	23,515
Cash flows from investing activities
Purchases of investments	(527,363)	(66,634)
Maturities of investments	86,105	71,980
Purchases of property and equipment	(23,491)	(10,087)
Acquisition of business, net of cash acquired	0	(14,438)
Net cash used in investing activities	(464,749)	(19,179)
Cash flows from financing activities
Common stock issued under stock plans, net	17,208	18,050
Payment of taxes related to the net share settlement of equity awards	(82,251)	(40,314)
Proceeds from issuance of convertible senior notes, net of issuance costs	780,180	335,601
Purchase of convertible senior notes capped call	(97,200)	(39,227)
Repurchase of common stock	(20,000)	(20,000)
Net cash provided by financing activities	597,937	254,110
Net increase in cash, cash equivalents and restricted cash	181,034	258,446
Cash, cash equivalents and restricted cash, beginning of period	375,945	126,963
Cash, cash equivalents and restricted cash, end of period	556,979	385,409
Supplemental cash flow data:
Interest	431	37
Income taxes	912	994
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	(2,325)	0
Non-cash investing activities:
Accrued purchases of long-lived assets	$ 5,170	$ 5,337

CONDENSED CONSOLIDATED STATEM_5

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - Reconciliation of cash, cash equivalents and restricted cash - USD ($) $ in Thousands	Jun. 30, 2019	Jun. 30, 2018
Statement of Cash Flows [Abstract]
Cash and cash equivalents	$ 555,792	$ 384,926
Restricted cash included in other current assets	121	0
Restricted cash included in other assets	1,066	483
Total cash, cash equivalents and restricted cash	$ 556,979	$ 385,409

Background and Basis of Present

Background and Basis of Presentation	6 Months Ended
	Jun. 30, 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 June 30, 2019 , the condensed consolidated statements of operations, the condensed consolidated statements of comprehensive loss, and the condensed consolidated statements of stockholder's equity for the three and six months ended June 30, 2019 and 2018 , the condensed consolidated statements of cash flows for the six months ended June 30, 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 June 30, 2019 , our results of operations, results of comprehensive loss, and stockholder's equity for the three and six months ended June 30, 2019 and 2018 and cash flows for the six months ended June 30, 2019 and 2018 . Our results of operations, stockholder's equity, and cash flows for the six months ended June 30, 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). We have changed the captions on our condensed consolidated statements of cash flows from “purchases of marketable securities” to “purchases of investments” and from “maturities of marketable securities” to “maturities of investments.” This change does not impact any current or previously reported results. 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. 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 2019 , the initial purchasers fully exercised their option to purchase $100 million of additional 2025 notes for aggregate total gross proceeds of $800 million . 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 sheets, 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, 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 May 2019, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) 2019-05, Financial Instruments—Credit Losses (Topic 326): Targeted Transition Relief. ASU 2019-05 provides entities with an option to irrevocably elect the fair value option for eligible instruments. In April 2019, the FASB issued ASU 2019-04, Codification Improvements to Topic 326, Financial Instruments—Credit Losses, Topic 815, Derivatives and Hedging, and Topic 825, Financial Instruments. ASU 2019-04 provides codification updates to ASU 2016-01 and ASU 2016-13. In June 2016, the FASB issued ASU 2016-13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments . ASU 2016-13 replaces the existing incurred loss impairment model with an expected loss model which requires the use of forward-looking information to calculate credit loss estimates. Early adoption is permitted and these guidance updates require a modified retrospective method of adoption. These guidance updates are effective for annual periods beginning after December 15, 2019, and we are currently in the process of evaluating the impact of these guidance updates. In August 2018, the FASB issued 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

Revenues	6 Months Ended
	Jun. 30, 2019
Revenue from Contract with Customer [Abstract]
Revenues	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 June 30, Change 2019 2018 $ % Chegg Services $ 80,307 $ 61,849 $ 18,458 30 % Required Materials 13,555 12,373 1,182 10 Total net revenues $ 93,862 $ 74,222 $ 19,640 26 Six Months Ended June 30, Change 2019 2018 $ % Chegg Services $ 155,599 $ 118,126 $ 37,473 32 % Required Materials 35,672 33,045 2,627 8 Total net revenues $ 191,271 $ 151,171 $ 40,100 27 During the three months ended June 30, 2019 , we recognized $19.9 million of revenues that were included in our deferred revenue balance as of March 31, 2019 . During the six months ended June 30, 2019 , we recognized $13.6 million of revenues that were included in our deferred revenue balance as of December 31, 2018 . During the three and six months ended June 30, 2019 , we recognized $0.7 million of previously deferred revenues recognized from performance obligations satisfied in previous periods related to variable consideration recognized from our agreement with our Required Materials print textbook partner. The aggregate amount of unsatisfied performance obligations is approximately $21.3 million as of June 30, 2019 , of which substantially all is expected to be recognized into revenues over the next year and the remainder within two years. Contract Balances The following table presents our accounts receivable, net and deferred revenue balances (in thousands, except percentages): Change June 30, 2019 December 31, 2018 $ % Accounts receivable, net $ 5,948 $ 12,733 $ (6,785 ) (53 )% Deferred revenue $ 18,821 $ 17,418 $ 1,403 8 % During the six months ended June 30, 2019 , our accounts receivable, net balance decreased by $6.8 million , or 53% , primarily due to an improvement in cash collections. During the six months ended June 30, 2019 , our deferred revenue balance increased by $1.4 million , or 8% , primarily due to increased bookings for our Chegg Study service and eTextbook rentals driven by the seasonality of our business. Our contract assets balance was immaterial as of June 30, 2019 and December 31, 2018 .

Net Loss Per Share

Net Loss Per Share	6 Months Ended
	Jun. 30, 2019
Earnings Per Share [Abstract]
Net Loss Per Share	Net Loss Per Share Basic net loss per share is computed by dividing the net loss by the weighted-average number of shares of common stock outstanding during the period. Diluted net loss per share is computed by giving effect to all potential shares of common stock, including 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 basic and diluted net loss per share (in thousands, except per share amounts): Three Months Ended June 30, Six Months Ended June 30, 2019 2018 2019 2018 Numerator: Net loss $ (2,029 ) $ (3,909 ) $ (6,347 ) $ (6,526 ) Denominator: Weighted average shares used to compute net loss per share, basic and diluted 118,790 112,738 117,766 111,826 Net loss per share, basic and diluted $ (0.02 ) $ (0.03 ) $ (0.05 ) $ (0.06 ) 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 June 30, Six Months Ended June 30, 2019 2018 2019 2018 Options to purchase common stock 2,753 4,369 3,006 4,321 RSUs and PSUs 3,787 7,079 5,394 8,128 Shares related to convertible senior notes 3,646 — 3,494 — Total common stock equivalents 10,186 11,448 11,894 12,449 Shares related to convertible senior notes represents the anti-dilutive impact of our issuance of $345 million in aggregate principal amount of our 2023 notes as the average price of our common stock during the three and six months ended June 30, 2019 was higher than the conversion price of $26.95 . While these shares are anti-dilutive during the three and six months ended June 30, 2019 , they may be dilutive in periods we report net income. However, as a result of the capped call transactions, there will be no economic dilution from the 2023 notes up to $40.68 , as exercise of the capped call instruments will reduce dilution from the 2023 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 $800 million in aggregate principal amount of our 2025 notes were anti-dilutive during the three and six months ended June 30, 2019 . The average price of our common stock during the three and six months ended June 30, 2019 was lower than the conversion price of our 2025 notes of $51.56 . See Note 7 for more information about our convertible senior notes.

Cash and Cash Equivalents, and

Cash and Cash Equivalents, and Investment	6 Months Ended
	Jun. 30, 2019
Cash and Cash Equivalents [Abstract]
Cash and Cash Equivalents, and Investment	Cash and Cash Equivalents, and Investments The following tables shows our cash and cash equivalents, and investments’ adjusted cost, unrealized gain, unrealized loss and fair value as of June 30, 2019 and December 31, 2018 (in thousands): June 30, 2019 Cost Unrealized Gain Unrealized Loss Fair Value Cash and cash equivalents: Cash $ 234,738 $ — $ — $ 234,738 Money market funds 268,689 — — 268,689 Commercial paper 52,375 — (10 ) 52,365 Total cash and cash equivalents $ 555,802 $ — $ (10 ) $ 555,792 Short-term investments: Commercial paper $ 58,717 $ 3 $ (12 ) $ 58,708 Corporate securities 146,074 195 (11 ) 146,258 U.S. treasury securities 44,398 31 — 44,429 Agency bonds 10,001 3 — 10,004 Total short-term investments $ 259,190 $ 232 $ (23 ) $ 259,399 Long-term investments: Corporate securities $ 228,389 $ 459 $ (172 ) $ 228,676 Agency bonds 60,000 6 — 60,006 Total long-term investments $ 288,389 $ 465 $ (172 ) $ 288,682 December 31, 2018 Cost Unrealized Gain Unrealized Loss Fair Value Cash and cash equivalents: Cash $ 351,345 $ — $ — $ 351,345 Money market funds 5,052 — — 5,052 Commercial paper 18,267 — — 18,267 Total cash and cash equivalents $ 374,664 $ — $ — $ 374,664 Short-term investments: Commercial paper $ 40,500 $ — $ (12 ) $ 40,488 Corporate securities 38,616 — (87 ) 38,529 U.S. treasury securities 14,333 — (5 ) 14,328 Total short-term investments $ 93,449 $ — $ (104 ) $ 93,345 Long-term investments: Corporate securities $ 14,429 $ 9 $ (14 ) $ 14,424 U.S. treasury securities 1,630 — (2 ) 1,628 Total long-term investments $ 16,059 $ 9 $ (16 ) $ 16,052 The adjusted cost and fair value of available-for-sale investments as of June 30, 2019 by contractual maturity were as follows (in thousands): Cost Fair Value Due in 1 year or less $ 311,565 $ 311,764 Due in 1-2 years 288,389 288,682 Investments not due at a single maturity date 268,689 268,689 Total $ 868,643 $ 869,135 Investments not due at a single maturity date in the preceding table consist of money market fund deposits. As of June 30, 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 eight months, and our investment policy generally limits the amount of credit exposure to any one issuer or industry sector. 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 and six months ended June 30, 2019 and 2018 , we did not recognize any other-than-impairment charges. Restricted Cash As of June 30, 2019 and December 31, 2018 , we had approximately $1.2 million and $1.3 million , respectively, of restricted cash that primarily 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 upon the term of the remaining restrictions. 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 and six months ended June 30, 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 similar investments of the same issuer during the three and six months ended June 30, 2019 and 2018 .

Fair Value Measurement

Fair Value Measurement	6 Months Ended
	Jun. 30, 2019
Fair Value Disclosures [Abstract]
Fair Value Measurement	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 June 30, 2019 and December 31, 2018 are classified based on the valuation technique level in the tables below (in thousands): June 30, 2019 Total Quoted Prices Significant Assets: Cash equivalents: Money market funds $ 268,689 $ 268,689 $ — Commercial paper 52,365 — 52,365 Short-term investments: Commercial paper 58,708 — 58,708 Corporate securities 146,258 — 146,258 U.S. treasury securities 44,429 44,429 — Agency bonds 10,004 — 10,004 Long-term investments: Corporate securities 228,676 — 228,676 Agency bonds 60,006 — 60,006 Total assets measured and recorded at fair value $ 869,135 $ 313,118 $ 556,017 December 31, 2018 Total Quoted Prices Significant 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 investments 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 investments 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 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 June 30, 2019 and December 31, 2018 are as follows (in thousands): June 30, 2019 December 31, 2018 Carrying Amount Estimated Fair Value Carrying Amount Estimated Fair Value 2025 notes $ 583,505 $ 803,864 $ — $ — 2023 notes 290,621 526,988 283,668 416,156 Convertible senior notes, net $ 874,126 $ 1,330,852 $ 283,668 $ 416,156 The carrying amount of the 2025 notes and 2023 notes as of June 30, 2019 was net of unamortized debt discount of $202.6 million and $48.6 million , respectively, and unamortized issuance costs of $13.9 million and $5.8 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

Goodwill and Intangible Assets

Goodwill and Intangible Assets	6 Months Ended
	Jun. 30, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	Goodwill and Intangible Assets Goodwill consists of the following (in thousands): Six Months Ended June 30, 2019 Year Ended December 31, 2018 Beginning balance $ 149,524 $ 125,272 Additions due to acquisitions — 24,673 Foreign currency translation adjustment (58 ) (421 ) Ending balance $ 149,466 $ 149,524 Intangible assets as of June 30, 2019 and December 31, 2018 consist of the following (in thousands, except weighted-average amortization period): June 30, 2019 Weighted-Average Amortization Period Gross Carrying Amount Accumulated Amortization Net Carrying Amount Developed technologies and content library 71 $ 31,667 $ (15,853 ) $ 15,814 Customer lists 47 9,970 (7,530 ) 2,440 Trade names 44 6,113 (5,462 ) 651 Non-compete agreements 31 2,018 (1,840 ) 178 Indefinite-lived trade name — 3,600 — 3,600 Foreign currency translation adjustment — (309 ) — (309 ) Total intangible assets 61 $ 53,059 $ (30,685 ) $ 22,374 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 and six months ended June 30, 2019 , amortization expense related to our acquired intangible assets totaled approximately $1.7 million and $3.5 million , respectively. During the three and six months ended June 30, 2018 , amortization expense related to our acquired intangible assets totaled approximately $1.4 million and $2.9 million , respectively. As of June 30, 2019 , the estimated future amortization expense related to our finite-lived intangible assets is as follows (in thousands): Remaining six months of 2019 $ 2,945 2020 4,816 2021 3,423 2022 2,943 2023 2,276 Thereafter 2,371 Total $ 18,774

Convertible Senior Notes

Convertible Senior Notes	6 Months Ended
	Jun. 30, 2019
Debt Disclosure [Abstract]
Convertible Senior Notes	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) and in April 2019 , the initial purchasers fully exercised their option to purchase $100 million of additional notes for aggregate total principal amount of $800 million . 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 $ 800,000 $ 345,000 Less initial purchasers’ discount (18,998 ) (8,625 ) Less other issuance costs (822 ) (757 ) Net proceeds $ 780,180 $ 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 and six months ended June 30, 2019 , the conditions allowing holders of the 2025 notes to convert had not been met and were therefore not convertible. During the three and six months ended June 30, 2019 , the conditions allowing holders of the 2023 notes to convert had been met and are therefore convertible. None of the holders of the 2023 notes elected to convert their notes into shares of our common stock during the three and six months ended June 30, 2019 . During the three months ended June 30, 2018, the conditions allowing holders of the notes to convert had not been met and were therefore not convertible. 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 $588.0 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 $212.0 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 sheets, 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 sheets 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 $19.8 million , consisting of the initial purchasers' discount of $19.0 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 $14.6 million and $7.6 million , respectively, were recorded as debt issuance cost, presented as a reduction to the notes on our condensed consolidated balance sheets, 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 $5.3 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): June 30, 2019 December 31, 2018 2025 Notes 2023 Notes 2023 Notes Principal $ 800,000 $ 345,000 $ 345,000 Unamortized debt discount (202,576 ) (48,600 ) (54,817 ) Unamortized issuance costs (13,919 ) (5,779 ) (6,515 ) Net carrying amount (liability) $ 583,505 $ 290,621 $ 283,668 The net carrying amount of the equity component of the notes is as follows (in thousands): June 30, 2019 December 31, 2018 2025 Notes 2023 Notes 2023 Notes Debt discount for conversion option $ 212,000 $ 64,193 $ 64,193 Issuance costs (5,253 ) (1,749 ) (1,749 ) Net carrying amount (equity) $ 206,747 $ 62,444 $ 62,444 As of June 30, 2019 , the remaining lives of the 2025 notes and 2023 notes are approximately 5.7 and 3.9 years, respectively, and are classified as long-term debt. Based on the closing price of our common stock of $38.59 on June 30, 2019 , the if-converted value of the 2025 notes was approximately $598.8 million which is less than the principal amount of $800 million by approximately $201.2 million and the if-converted value of the 2023 notes was approximately $494.0 million which exceeds the principal amount of $345 million by approximately $149.0 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 tables set forth the total interest expense recognized related to the notes (in thousands): Three Months Ended June 30, 2019 2018 2025 Notes 2023 Notes 2023 Notes Contractual interest expense $ 251 $ 215 $ 210 Amortization of debt discount 8,914 3,125 3,057 Amortization of issuance costs 613 368 364 Total interest expense $ 9,778 $ 3,708 $ 3,631 Six Months Ended June 30, 2019 2018 2025 Notes 2023 Notes 2023 Notes Contractual interest expense $ 265 $ 428 $ 210 Amortization of debt discount 9,424 6,216 3,057 Amortization of issuance costs 648 737 364 Total interest expense $ 10,337 $ 7,381 $ 3,631 Capped Call Transactions Concurrently with the offering of the 2025 notes and 2023 notes, we used $97.2 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 15,516,480 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 sheets 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 our 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 each respective 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

Leases

Leases	6 Months Ended
	Jun. 30, 2019
Leases [Abstract]
Leases	Leases We have operating leases for corporate offices worldwide, which expire at various dates through 2024 . Our primary operating lease commitments at June 30, 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 June 30, 2019 , we had operating lease ROU assets of $14.8 million and operating lease liabilities of $19.0 million . As of June 30, 2019 , we do not have finance leases recorded on our condensed consolidated balance sheet. As of June 30, 2019 , our weighted average remaining lease term was 4.1 years . During the three and six months ended June 30, 2019 , our weighted average discount rate was 4.7% . Operating lease expense, net of immaterial sublease income, was approximately $1.2 million and $2.5 million during the three and six months ended June 30, 2019 , respectively. Variable lease cost was immaterial during the three and six months ended June 30, 2019 . We did not record short term lease cost during the three and six months ended June 30, 2019 . The aggregate future minimum lease payments and reconciliation to lease liabilities as of June 30, 2019 , are as follows (in thousands): June 30, 2019 Remaining six months of 2019 $ 2,948 2020 5,202 2021 4,682 2022 3,931 2023 3,424 Thereafter 788 Total future minimum lease payments 20,975 Less imputed interest (1,958 ) Total lease liabilities $ 19,017 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

Commitments and Contingencies	6 Months Ended
	Jun. 30, 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. 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”). We filed a Motion to Dismiss on February 19, 2019 and an initial status conference was held on March 1, 2019. On July 3, 2019, an order was issued staying proceedings pending determination of the Motion to Dismiss. The complaint seeks unspecified compensatory damages. We have not recorded any amounts related to the above matter, as we do not believe that a loss is probable. 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 condensed 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 this action, including a judgment or settlement, may cause a material adverse effect on our future business, operating results and/or financial condition.

Guarantees and Indemnifications

Guarantees and Indemnifications	6 Months Ended
	Jun. 30, 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 June 30, 2019 .

Stockholders' Equity

Stockholders' Equity	6 Months Ended
	Jun. 30, 2019
Share-based Payment Arrangement [Abstract]
Stockholders' Equity	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 June 30, Six Months Ended June 30, 2019 2018 2019 2018 Cost of revenues $ 74 $ 103 $ 199 $ 197 Research and development 5,218 3,529 10,135 7,662 Sales and marketing 1,754 1,730 3,562 3,319 General and administrative 8,406 6,681 16,594 12,507 Total share-based compensation expense $ 15,452 $ 12,043 $ 30,490 $ 23,685 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 1,749,113 39.53 Released (4,812,355 ) 9.20 Canceled (979,126 ) 9.49 Balance at June 30, 2019 6,762,440 $ 21.27 As of June 30, 2019 , our total unrecognized share-based compensation expense related to RSUs and PSUs was approximately $92.7 million , which will be recognized over the remaining weighted-average vesting period of approximately 1.7 years .

Income Taxes

Income Taxes	6 Months Ended
	Jun. 30, 2019
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes We recorded an income tax provision of approximately $0.6 million and $1.2 million during the three and six months ended June 30, 2019 , respectively, primarily due to state and foreign income tax expense. We recorded an income tax provision of approximately $0.4 million and $1.0 million during the three and six months ended June 30, 2018 , respectively, primarily due to foreign and state tax expense offset by federal and state tax benefits related to deferred tax liabilities of acquired intangible assets.

Restructuring Charges

Restructuring Charges	6 Months Ended
	Jun. 30, 2019
Restructuring and Related Activities [Abstract]
Restructuring Charges	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 assumed responsibility for managing, renewing, and maintaining our existing university contracts and became 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 4 months. 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 69 — — 69 Cash payments (185 ) — — (185 ) Balance at June 30, 2019 $ 30 $ — $ — $ 30

Related-Party Transactions

Related-Party Transactions	6 Months Ended
	Jun. 30, 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 and six months ended June 30, 2019 , we had purchases of $0.4 million and $1.4 million , respectively, and during the three and six months ended June 30, 2018 , we had purchases of $0.6 million and $2.3 million , respectively, from Adobe. We had no revenues during the three and six months ended June 30, 2019 from Adobe. We had no revenues during the three months ended June 30, 2018 and $0.1 million of revenues during the six months ended June 30, 2018 from Adobe. We had no payables as of June 30, 2019 and an immaterial amount as of December 31, 2018 to Adobe. We had no outstanding receivables as of June 30, 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 and six months ended June 30, 2019 , we had purchases of $1.5 million and $10.6 million , respectively, and during the three and six months ended June 30, 2018 , we had purchases of $1.4 million and $6.5 million , respectively, from Cengage. We had $0.4 million and $1.6 million of revenues during the three and six months ended June 30, 2019 , respectively, and $0.1 million and $2.0 million of revenues during the three and six months ended June 30, 2018 , respectively, from Cengage. We had an immaterial amount and $0.1 million in payables as of June 30, 2019 and December 31, 2018 , respectively, to Cengage. We had an immaterial amount of outstanding receivables as of June 30, 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 and six months ended June 30, 2019 , we incurred payment processing fees of $0.4 million and $0.8 million , respectively, and during the three and six months ended June 30, 2018 , we incurred processing fees of $0.2 million and $0.6 million , respectively, to PayPal. One of our board members is also a member of the Board of Directors of Synack, Inc. (Synack). During the six months ended June 30, 2019 , we had purchases of $0.3 million of services from Synack.

Background and Basis of Prese_2

Background and Basis of Presentation (Policies)	6 Months Ended
	Jun. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation The accompanying condensed consolidated balance sheet as of June 30, 2019 , the condensed consolidated statements of operations, the condensed consolidated statements of comprehensive loss, and the condensed consolidated statements of stockholder's equity for the three and six months ended June 30, 2019 and 2018 , the condensed consolidated statements of cash flows for the six months ended June 30, 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 June 30, 2019 , our results of operations, results of comprehensive loss, and stockholder's equity for the three and six months ended June 30, 2019 and 2018 and cash flows for the six months ended June 30, 2019 and 2018 . Our results of operations, stockholder's equity, and cash flows for the six months ended June 30, 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). We have changed the captions on our condensed consolidated statements of cash flows from “purchases of marketable securities” to “purchases of investments” and from “maturities of marketable securities” to “maturities of investments.” This change does not impact any current or previously reported results. 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.
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 2019 , the initial purchasers fully exercised their option to purchase $100 million of additional 2025 notes for aggregate total gross proceeds of $800 million . 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 sheets, 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, 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 May 2019, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) 2019-05, Financial Instruments—Credit Losses (Topic 326): Targeted Transition Relief. ASU 2019-05 provides entities with an option to irrevocably elect the fair value option for eligible instruments. In April 2019, the FASB issued ASU 2019-04, Codification Improvements to Topic 326, Financial Instruments—Credit Losses, Topic 815, Derivatives and Hedging, and Topic 825, Financial Instruments. ASU 2019-04 provides codification updates to ASU 2016-01 and ASU 2016-13. In June 2016, the FASB issued ASU 2016-13, Financial Instruments—Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments . ASU 2016-13 replaces the existing incurred loss impairment model with an expected loss model which requires the use of forward-looking information to calculate credit loss estimates. Early adoption is permitted and these guidance updates require a modified retrospective method of adoption. These guidance updates are effective for annual periods beginning after December 15, 2019, and we are currently in the process of evaluating the impact of these guidance updates. In August 2018, the FASB issued 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)

Revenues (Tables)	6 Months Ended
	Jun. 30, 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 June 30, Change 2019 2018 $ % Chegg Services $ 80,307 $ 61,849 $ 18,458 30 % Required Materials 13,555 12,373 1,182 10 Total net revenues $ 93,862 $ 74,222 $ 19,640 26 Six Months Ended June 30, Change 2019 2018 $ % Chegg Services $ 155,599 $ 118,126 $ 37,473 32 % Required Materials 35,672 33,045 2,627 8 Total net revenues $ 191,271 $ 151,171 $ 40,100 27
Schedule of Accounts Receivable	The following table presents our accounts receivable, net and deferred revenue balances (in thousands, except percentages): Change June 30, 2019 December 31, 2018 $ % Accounts receivable, net $ 5,948 $ 12,733 $ (6,785 ) (53 )% Deferred revenue $ 18,821 $ 17,418 $ 1,403 8 %

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	6 Months Ended
	Jun. 30, 2019
Earnings Per Share [Abstract]
Schedule of Earnings Per Share, Basic and Diluted	The following table sets forth the computation of basic and diluted net loss per share (in thousands, except per share amounts): Three Months Ended June 30, Six Months Ended June 30, 2019 2018 2019 2018 Numerator: Net loss $ (2,029 ) $ (3,909 ) $ (6,347 ) $ (6,526 ) Denominator: Weighted average shares used to compute net loss per share, basic and diluted 118,790 112,738 117,766 111,826 Net loss per share, basic and diluted $ (0.02 ) $ (0.03 ) $ (0.05 ) $ (0.06 )
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 June 30, Six Months Ended June 30, 2019 2018 2019 2018 Options to purchase common stock 2,753 4,369 3,006 4,321 RSUs and PSUs 3,787 7,079 5,394 8,128 Shares related to convertible senior notes 3,646 — 3,494 — Total common stock equivalents 10,186 11,448 11,894 12,449

Cash and Cash Equivalents, an_2

Cash and Cash Equivalents, and Investment (Tables)	6 Months Ended
	Jun. 30, 2019
Cash and Cash Equivalents [Abstract]
Cash, Cash Equivalents and Investments	The following tables shows our cash and cash equivalents, and investments’ adjusted cost, unrealized gain, unrealized loss and fair value as of June 30, 2019 and December 31, 2018 (in thousands): June 30, 2019 Cost Unrealized Gain Unrealized Loss Fair Value Cash and cash equivalents: Cash $ 234,738 $ — $ — $ 234,738 Money market funds 268,689 — — 268,689 Commercial paper 52,375 — (10 ) 52,365 Total cash and cash equivalents $ 555,802 $ — $ (10 ) $ 555,792 Short-term investments: Commercial paper $ 58,717 $ 3 $ (12 ) $ 58,708 Corporate securities 146,074 195 (11 ) 146,258 U.S. treasury securities 44,398 31 — 44,429 Agency bonds 10,001 3 — 10,004 Total short-term investments $ 259,190 $ 232 $ (23 ) $ 259,399 Long-term investments: Corporate securities $ 228,389 $ 459 $ (172 ) $ 228,676 Agency bonds 60,000 6 — 60,006 Total long-term investments $ 288,389 $ 465 $ (172 ) $ 288,682 December 31, 2018 Cost Unrealized Gain Unrealized Loss Fair Value Cash and cash equivalents: Cash $ 351,345 $ — $ — $ 351,345 Money market funds 5,052 — — 5,052 Commercial paper 18,267 — — 18,267 Total cash and cash equivalents $ 374,664 $ — $ — $ 374,664 Short-term investments: Commercial paper $ 40,500 $ — $ (12 ) $ 40,488 Corporate securities 38,616 — (87 ) 38,529 U.S. treasury securities 14,333 — (5 ) 14,328 Total short-term investments $ 93,449 $ — $ (104 ) $ 93,345 Long-term investments: Corporate securities $ 14,429 $ 9 $ (14 ) $ 14,424 U.S. treasury securities 1,630 — (2 ) 1,628 Total long-term investments $ 16,059 $ 9 $ (16 ) $ 16,052
Schedule of Available-for-sale Securities Reconciliation	The adjusted cost and fair value of available-for-sale investments as of June 30, 2019 by contractual maturity were as follows (in thousands): Cost Fair Value Due in 1 year or less $ 311,565 $ 311,764 Due in 1-2 years 288,389 288,682 Investments not due at a single maturity date 268,689 268,689 Total $ 868,643 $ 869,135

Fair Value Measurement (Tables)

Fair Value Measurement (Tables)	6 Months Ended
	Jun. 30, 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 June 30, 2019 and December 31, 2018 are classified based on the valuation technique level in the tables below (in thousands): June 30, 2019 Total Quoted Prices Significant Assets: Cash equivalents: Money market funds $ 268,689 $ 268,689 $ — Commercial paper 52,365 — 52,365 Short-term investments: Commercial paper 58,708 — 58,708 Corporate securities 146,258 — 146,258 U.S. treasury securities 44,429 44,429 — Agency bonds 10,004 — 10,004 Long-term investments: Corporate securities 228,676 — 228,676 Agency bonds 60,006 — 60,006 Total assets measured and recorded at fair value $ 869,135 $ 313,118 $ 556,017 December 31, 2018 Total Quoted Prices Significant 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 June 30, 2019 and December 31, 2018 are as follows (in thousands): June 30, 2019 December 31, 2018 Carrying Amount Estimated Fair Value Carrying Amount Estimated Fair Value 2025 notes $ 583,505 $ 803,864 $ — $ — 2023 notes 290,621 526,988 283,668 416,156 Convertible senior notes, net $ 874,126 $ 1,330,852 $ 283,668 $ 416,156

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	6 Months Ended
	Jun. 30, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Goodwill	Goodwill consists of the following (in thousands): Six Months Ended June 30, 2019 Year Ended December 31, 2018 Beginning balance $ 149,524 $ 125,272 Additions due to acquisitions — 24,673 Foreign currency translation adjustment (58 ) (421 ) Ending balance $ 149,466 $ 149,524
Finite-Lived Intangible Assets	Intangible assets as of June 30, 2019 and December 31, 2018 consist of the following (in thousands, except weighted-average amortization period): June 30, 2019 Weighted-Average Amortization Period Gross Carrying Amount Accumulated Amortization Net Carrying Amount Developed technologies and content library 71 $ 31,667 $ (15,853 ) $ 15,814 Customer lists 47 9,970 (7,530 ) 2,440 Trade names 44 6,113 (5,462 ) 651 Non-compete agreements 31 2,018 (1,840 ) 178 Indefinite-lived trade name — 3,600 — 3,600 Foreign currency translation adjustment — (309 ) — (309 ) Total intangible assets 61 $ 53,059 $ (30,685 ) $ 22,374 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 June 30, 2019 and December 31, 2018 consist of the following (in thousands, except weighted-average amortization period): June 30, 2019 Weighted-Average Amortization Period Gross Carrying Amount Accumulated Amortization Net Carrying Amount Developed technologies and content library 71 $ 31,667 $ (15,853 ) $ 15,814 Customer lists 47 9,970 (7,530 ) 2,440 Trade names 44 6,113 (5,462 ) 651 Non-compete agreements 31 2,018 (1,840 ) 178 Indefinite-lived trade name — 3,600 — 3,600 Foreign currency translation adjustment — (309 ) — (309 ) Total intangible assets 61 $ 53,059 $ (30,685 ) $ 22,374 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 June 30, 2019 , the estimated future amortization expense related to our finite-lived intangible assets is as follows (in thousands): Remaining six months of 2019 $ 2,945 2020 4,816 2021 3,423 2022 2,943 2023 2,276 Thereafter 2,371 Total $ 18,774

Convertible Senior Notes (Table

Convertible Senior Notes (Tables)	6 Months Ended
	Jun. 30, 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 $ 800,000 $ 345,000 Less initial purchasers’ discount (18,998 ) (8,625 ) Less other issuance costs (822 ) (757 ) Net proceeds $ 780,180 $ 335,618
Schedule of Debt	The net carrying amount of the liability component of the notes is as follows (in thousands): June 30, 2019 December 31, 2018 2025 Notes 2023 Notes 2023 Notes Principal $ 800,000 $ 345,000 $ 345,000 Unamortized debt discount (202,576 ) (48,600 ) (54,817 ) Unamortized issuance costs (13,919 ) (5,779 ) (6,515 ) Net carrying amount (liability) $ 583,505 $ 290,621 $ 283,668 The net carrying amount of the equity component of the notes is as follows (in thousands): June 30, 2019 December 31, 2018 2025 Notes 2023 Notes 2023 Notes Debt discount for conversion option $ 212,000 $ 64,193 $ 64,193 Issuance costs (5,253 ) (1,749 ) (1,749 ) Net carrying amount (equity) $ 206,747 $ 62,444 $ 62,444
Schedule Of Interest Expense Recognized	The following tables set forth the total interest expense recognized related to the notes (in thousands): Three Months Ended June 30, 2019 2018 2025 Notes 2023 Notes 2023 Notes Contractual interest expense $ 251 $ 215 $ 210 Amortization of debt discount 8,914 3,125 3,057 Amortization of issuance costs 613 368 364 Total interest expense $ 9,778 $ 3,708 $ 3,631 Six Months Ended June 30, 2019 2018 2025 Notes 2023 Notes 2023 Notes Contractual interest expense $ 265 $ 428 $ 210 Amortization of debt discount 9,424 6,216 3,057 Amortization of issuance costs 648 737 364 Total interest expense $ 10,337 $ 7,381 $ 3,631

Leases (Tables)

Leases (Tables)	6 Months Ended
	Jun. 30, 2019
Leases [Abstract]
Lessee, Operating Lease, Liability, Maturity	The aggregate future minimum lease payments and reconciliation to lease liabilities as of June 30, 2019 , are as follows (in thousands): June 30, 2019 Remaining six months of 2019 $ 2,948 2020 5,202 2021 4,682 2022 3,931 2023 3,424 Thereafter 788 Total future minimum lease payments 20,975 Less imputed interest (1,958 ) Total lease liabilities $ 19,017 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)

Stockholders' Equity (Tables)	6 Months Ended
	Jun. 30, 2019
Share-based Payment Arrangement [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 June 30, Six Months Ended June 30, 2019 2018 2019 2018 Cost of revenues $ 74 $ 103 $ 199 $ 197 Research and development 5,218 3,529 10,135 7,662 Sales and marketing 1,754 1,730 3,562 3,319 General and administrative 8,406 6,681 16,594 12,507 Total share-based compensation expense $ 15,452 $ 12,043 $ 30,490 $ 23,685
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 1,749,113 39.53 Released (4,812,355 ) 9.20 Canceled (979,126 ) 9.49 Balance at June 30, 2019 6,762,440 $ 21.27

Restructuring Charges (Tables)

Restructuring Charges (Tables)	6 Months Ended
	Jun. 30, 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 69 — — 69 Cash payments (185 ) — — (185 ) Balance at June 30, 2019 $ 30 $ — $ — $ 30

Background and Basis of Prese_3

Background and Basis of Presentation (Details) - USD ($)	1 Months Ended
	Apr. 30, 2019	Apr. 30, 2018	Jun. 30, 2019	Mar. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Right of use assets			$ 14,756,000			$ 0
Operating lease liability			19,017,000
Senior Notes | 0.125% Convertible Senior Notes Due 2025
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Face value	$ 100,000,000		800,000,000	$ 700,000,000
Proceeds from issuance of debt	$ 800,000,000
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
Proceeds from issuance of debt		$ 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)

Revenues (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Total net revenues	$ 93,862	$ 74,222	$ 191,271	$ 151,171
Change in total net revenues	$ 19,640		$ 40,100
Change in total net revenues, percent	26.00%		27.00%
Contract with customer, liability, revenue recognized	$ 19,900		$ 13,600
Contract with customer, liability, revenue recognized, prior period	700
Aggregate amount of unsatisfied performance obligations	21,300		21,300
Accounts receivable, net	5,948		5,948		$ 12,733
Change in accounts receivable			$ (6,785)
Change in accounts receivable, percent			(53.00%)
Deferred revenue	18,821		$ 18,821		$ 17,418
Change in deferred revenue			$ 1,403
Change in deferred revenue, percent			8.00%
Chegg Services
Disaggregation of Revenue [Line Items]
Total net revenues	80,307	61,849	$ 155,599	118,126
Change in total net revenues	$ 18,458		$ 37,473
Change in total net revenues, percent	30.00%		32.00%
Required Materials
Disaggregation of Revenue [Line Items]
Total net revenues	$ 13,555	$ 12,373	$ 35,672	$ 33,045
Change in total net revenues	$ 1,182		$ 2,627
Change in total net revenues, percent	10.00%		8.00%

Net Loss Per Share - Computatio

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		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Numerator:
Net loss	$ (2,029)	$ (3,909)	$ (6,347)	$ (6,526)
Denominator:
Weighted average shares used to compute net loss per share, basic and diluted (in shares)	118,790	112,738	117,766	111,826
Net loss per share, basic and diluted (in dollars per share)	$ (0.02)	$ (0.03)	$ (0.05)	$ (0.06)

Net Loss Per Share - Shares Exc

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		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Apr. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Apr. 30, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total common stock equivalents (in shares)	10,186	11,448	11,894	12,449
Options to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total common stock equivalents (in shares)	2,753	4,369	3,006	4,321
RSUs and PSUs
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total common stock equivalents (in shares)	3,787	7,079	5,394	8,128
Shares related to convertible senior notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total common stock equivalents (in shares)	3,646	0	3,494	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	$ 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	$ 800,000,000		$ 800,000,000		$ 100,000,000	$ 700,000,000
Conversion price	$ 51.56		$ 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		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		$ 79.32

Cash and Cash Equivalents, an_3

Cash and Cash Equivalents, and Investment - Additional Information (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2019	Dec. 31, 2018	Oct. 31, 2018
Schedule of Investments [Line Items]
Weighted average maturity	8 months
Restricted cash	$ 1.2	$ 1.3
Cost method investment			$ 10
Other Assets | Equity Investments
Schedule of Investments [Line Items]
Investments	$ 3

Cash and Cash Equivalents, an_4

Cash and Cash Equivalents, and Investment - Schedule of Available For Sale Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Cost	$ 868,643
Fair Value	869,135
Cash and cash equivalents:
Debt Securities, Available-for-sale [Line Items]
Cost	555,802	$ 374,664
Unrealized Gain	0	0
Unrealized Loss	(10)	0
Fair Value	555,792	374,664
Short-term investments:
Debt Securities, Available-for-sale [Line Items]
Cost	259,190	93,449
Unrealized Gain	232	0
Unrealized Loss	(23)	(104)
Fair Value	259,399	93,345
Long-term investments:
Debt Securities, Available-for-sale [Line Items]
Cost	288,389	16,059
Unrealized Gain	465	9
Unrealized Loss	(172)	(16)
Fair Value	288,682	16,052
Commercial paper | Short-term investments:
Debt Securities, Available-for-sale [Line Items]
Cost	58,717	40,500
Unrealized Gain	3	0
Unrealized Loss	(12)	(12)
Fair Value	58,708	40,488
Corporate securities | Short-term investments:
Debt Securities, Available-for-sale [Line Items]
Cost	146,074	38,616
Unrealized Gain	195	0
Unrealized Loss	(11)	(87)
Fair Value	146,258	38,529
Corporate securities | Long-term investments:
Debt Securities, Available-for-sale [Line Items]
Cost	228,389	14,429
Unrealized Gain	459	9
Unrealized Loss	(172)	(14)
Fair Value	228,676	14,424
U.S. treasury securities | Short-term investments:
Debt Securities, Available-for-sale [Line Items]
Cost	44,398	14,333
Unrealized Gain	31	0
Unrealized Loss	0	(5)
Fair Value	44,429	14,328
U.S. treasury securities | Long-term investments:
Debt Securities, Available-for-sale [Line Items]
Cost		1,630
Unrealized Gain		0
Unrealized Loss		(2)
Fair Value		1,628
Agency bonds | Short-term investments:
Debt Securities, Available-for-sale [Line Items]
Cost	10,001
Unrealized Gain	3
Unrealized Loss	0
Fair Value	10,004
Agency bonds | Long-term investments:
Debt Securities, Available-for-sale [Line Items]
Cost	60,000
Unrealized Gain	6
Unrealized Loss	0
Fair Value	60,006
Cash | Cash and cash equivalents:
Debt Securities, Available-for-sale [Line Items]
Cost	234,738	351,345
Unrealized Gain	0	0
Unrealized Loss	0	0
Fair Value	234,738	351,345
Money market funds | Cash and cash equivalents:
Debt Securities, Available-for-sale [Line Items]
Cost	268,689	5,052
Unrealized Gain	0	0
Unrealized Loss	0	0
Fair Value	268,689	5,052
Commercial paper | Cash and cash equivalents:
Debt Securities, Available-for-sale [Line Items]
Cost	52,375	18,267
Unrealized Gain	0	0
Unrealized Loss	(10)	0
Fair Value	$ 52,365	$ 18,267

Cash and Cash Equivalents, an_5

Cash and Cash Equivalents, and Investment - Contractual Maturity (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2019USD ($)
Cash and Cash Equivalents [Abstract]
Due in 1 year or less, Cost	$ 311,565
Due in 1-2 years, Cost	288,389
Investments not due at a single maturity date, Cost	268,689
Cost	868,643
Due in 1 year or less, Fair Value	311,764
Due in 1-2 years, Fair Value	288,682
Investments not due at a single maturity date, Fair Value	268,689
Total, Fair Value	$ 869,135
Weighted average maturity	8 months

Fair Value Measurement - Financ

Fair Value Measurement - Financial Instruments (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	$ 259,399	$ 93,345
Long-term investments	288,682	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	869,135	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	313,118	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	556,017	111,708
Commercial paper | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	58,708	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	58,708	40,488
Corporate securities | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	146,258	38,529
Long-term investments	228,676	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	146,258	38,529
Long-term investments	228,676	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	44,429	14,328
Long-term investments		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	44,429	14,328
Long-term investments		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
Agency bonds | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	10,004
Long-term investments	60,006
Agency bonds | 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
Long-term investments	0
Agency bonds | 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	10,004
Long-term investments	60,006
Money market funds | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	268,689	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	268,689	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	52,365	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	$ 52,365	$ 18,267

Fair Value Measurement - Debt (

Fair Value Measurement - Debt (Details) - Senior Notes - USD ($) $ in Thousands	Jun. 30, 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	$ 874,126	$ 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	1,330,852	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	202,576
Unamortized issuance costs	13,919
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	583,505	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	803,864	0
0.25% Convertible Senior Notes Due 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unamortized debt discount	48,600	54,817
Unamortized issuance costs	5,779	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	290,621	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	$ 526,988	$ 416,156

Goodwill and Intangible Asset_2

Goodwill and Intangible Assets - Goodwill (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Goodwill [Roll Forward]
Beginning balance	$ 149,524	$ 125,272
Additions due to acquisitions	0	24,673
Foreign currency translation adjustment	(58)	(421)
Ending balance	$ 149,466	$ 149,524

Goodwill and Intangible Asset_3

Goodwill and Intangible Assets - Finite-lived and Indefinite-lived Intangibe Assets (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Finite Lived Intangible Assets [Line Items]
Weighted-Average Amortization Period	61 months	61 months
Accumulated Amortization	$ (30,685)	$ (27,182)
Net Carrying Amount	18,774
Indefinite-lived trade name	3,600	3,600
Foreign currency translation adjustment	(309)	(271)
Total intangible assets, gross carrying amount	53,059	53,097
Intangible assets, net	$ 22,374	$ 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	(15,853)	(13,737)
Net Carrying Amount	$ 15,814	$ 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	(7,530)	(6,847)
Net Carrying Amount	$ 2,440	$ 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	(5,462)	(4,863)
Net Carrying Amount	$ 651	$ 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	(1,840)	(1,735)
Net Carrying Amount	$ 178	$ 283

Goodwill and Intangible Asset_4

Goodwill and Intangible Assets - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Acquisition-Related Intangible Assets
Finite Lived Intangible Assets [Line Items]
Amortization expense of acquisition related to acquired intangible assets	$ 1.7	$ 1.4	$ 3.5	$ 2.9

Goodwill and Intangible Asset_5

Goodwill and Intangible Assets - Estimated Future Amortization Expense Related to Intangible Assets (Details) $ in Thousands	Jun. 30, 2019USD ($)
Goodwill and Intangible Assets Disclosure [Abstract]
Remaining six months of 2019	$ 2,945
2020	4,816
2021	3,423
2022	2,943
2023	2,276
Thereafter	2,371
Net Carrying Amount	$ 18,774

Convertible Senior Notes - Conv

Convertible Senior Notes - Convertible Senior Notes (Details)	Jun. 30, 2018USD ($)	Apr. 30, 2019USD ($)	Mar. 31, 2019USD ($)shares	Apr. 30, 2018USD ($)day$ / sharesshares	Jun. 30, 2019USD ($)$ / shares	Jun. 30, 2018USD ($)	Dec. 31, 2018USD ($)
Debt Instrument [Line Items]
Net proceeds					$ 780,180,000	$ 335,601,000
Senior Notes | 0.125% Convertible Senior Notes Due 2025
Debt Instrument [Line Items]
Face value		$ 100,000,000	$ 700,000,000		$ 800,000,000
Proceeds from issuance of debt		800,000,000
Interest rate, stated percentage			0.125%
Less initial purchasers’ discount		(18,998,000)
Less other issuance costs		(822,000)
Net proceeds		$ 780,180,000
Conversion price | $ / shares					$ 51.56
Equity component					$ 206,747,000
Debt issuance costs					$ (19,800,000)
Debt instrument, remaining useful life					5 years 8 months 12 days
Debt conversion, converted instrument, amount	$ 598,800,000
Debt instrument, if-converted value less than principal			$ (201,200,000)
Interest rate, effective percentage					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
Proceeds from issuance of debt				$ 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				$ 64,200,000	$ 62,444,000		$ 62,444,000
Debt issuance costs				(9,400,000)
Debt instrument, remaining useful life					3 years 10 months 24 days
Share price (in dollars per share) | $ / shares					$ 38.59
Debt conversion, converted instrument, amount	$ 494,000,000
Debt instrument, if-converted value in excess of principal				$ 149,000,000
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					$ 588,000,000
Equity component					212,000,000
Debt issuance costs					(14,600,000)
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					$ (5,300,000)
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			$ 97,200,000
Conversion price | $ / shares					$ 79.32
Shares covered by capped call transactions (in shares) | shares			15,516,480
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
Shares covered by capped call transactions (in shares) | shares				12,801,260

Convertible Senior Notes - Net

Convertible Senior Notes - Net Carrying Amount (Details) - Senior Notes - USD ($)	Jun. 30, 2019	Apr. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Apr. 30, 2018
0.125% Convertible Senior Notes Due 2025
Debt Instrument [Line Items]
Principal	$ 800,000,000	$ 100,000,000	$ 700,000,000
Unamortized debt discount	(202,576,000)
Unamortized issuance costs	(13,919,000)
Debt discount for conversion option	212,000,000
Issuance costs	(5,253,000)
Net carrying amount (equity)	206,747,000
0.25% Convertible Senior Notes Due 2023
Debt Instrument [Line Items]
Principal	345,000,000			$ 345,000,000	$ 345,000,000
Unamortized debt discount	(48,600,000)			(54,817,000)
Unamortized issuance costs	(5,779,000)			(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 (equity)	62,444,000			62,444,000	$ 64,200,000
Carrying Amount | Fair Value, Measurements, Nonrecurring
Debt Instrument [Line Items]
Net carrying amount (liability)	874,126,000			283,668,000
Carrying Amount | Fair Value, Measurements, Nonrecurring | 0.125% Convertible Senior Notes Due 2025
Debt Instrument [Line Items]
Net carrying amount (liability)	583,505,000			0
Carrying Amount | Fair Value, Measurements, Nonrecurring | 0.25% Convertible Senior Notes Due 2023
Debt Instrument [Line Items]
Net carrying amount (liability)	$ 290,621,000			$ 283,668,000

Convertible Senior Notes - Inte

Convertible Senior Notes - Interest Expense Recognized (Details) - Senior Notes - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
0.125% Convertible Senior Notes Due 2025
Debt Instrument [Line Items]
Contractual interest expense	$ 251		$ 265
Amortization of debt discount	8,914		9,424
Amortization of issuance costs	613		648
Total interest expense	9,778		10,337
0.25% Convertible Senior Notes Due 2023
Debt Instrument [Line Items]
Contractual interest expense	215	$ 210	428	$ 210
Amortization of debt discount	3,125	3,057	6,216	3,057
Amortization of issuance costs	368	364	737	364
Total interest expense	$ 3,708	$ 3,631	$ 7,381	$ 3,631

Leases - Additional Information

Leases - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019	Dec. 31, 2018
Leases [Abstract]
Right of use assets	$ 14,756	$ 14,756	$ 0
Operating lease liability	$ 19,017	$ 19,017
Weighted average remaining lease term for operating lease	4 years 1 month 6 days	4 years 1 month 6 days
Weighted average discount rate used to determine the operating lease liability	4.70%	4.70%
Lease expense	$ 1,200	$ 2,500

Leases - Maturities of Operatin

Leases - Maturities of Operating Lease Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Leases [Abstract]
Remaining six months of 2019	$ 2,948
2020	5,202
2021	4,682
2022	3,931
2023	3,424
2024	788
Total future minimum lease payments	20,975
Less imputed interest	(1,958)
Total lease liabilities	$ 19,017
2019		$ 5,222
2020		5,251
2021		4,775
2022		3,999
2023		3,421
Thereafter		788
Total		$ 23,456

Stockholders' Equity - Share-ba

Stockholders' Equity - Share-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Share-based compensation expense	$ 15,452	$ 12,043	$ 30,490	$ 23,685
Cost of revenues
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Share-based compensation expense	74	103	199	197
Research and development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Share-based compensation expense	5,218	3,529	10,135	7,662
Sales and marketing
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Share-based compensation expense	1,754	1,730	3,562	3,319
General and administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Share-based compensation expense	$ 8,406	$ 6,681	$ 16,594	$ 12,507

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	6 Months Ended
	Mar. 31, 2019	Jun. 30, 2019
RSUs and PSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation costs related to restricted stock units		$ 92.7
Weighted average vesting period for recognition of compensation expense		1 year 8 months 12 days
Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares repurchased (in shares)	504,286
Share price (in dollars per share)		$ 39.66

Stockholders' Equity - Summary

Stockholders' Equity - Summary of Restricted Stock Unit Activity (Details) - RSUs and PSUs	6 Months Ended
	Jun. 30, 2019$ / sharesshares
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	1,749,113
Number of RSUs and PSUs, Released (shares) | shares	(4,812,355)
Number of RSUs and PSUs, Canceled (shares) | shares	(979,126)
Number of RSUs and PSUs Outstanding, Ending (shares) | shares	6,762,440
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	39.53
Weighted Average Grant Date Fair Value, Released (in dollars per share) | $ / shares	9.20
Weighted Average Grant Date Fair Value, Canceled (in dollars per share) | $ / shares	9.49
Weighted Average Grant Date Fair Value, Ending balance (in dollars per share) | $ / shares	$ 21.27

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Income Tax Disclosure [Abstract]
Provision for income taxes	$ 583	$ 428	$ 1,209	$ 969

Restructuring Charges - Narrati

Restructuring Charges - Narrative (Details)	6 Months Ended
	Jun. 30, 2019position
2017 Restructuring Plan | Workforce Reduction Costs
Restructuring Cost and Reserve [Line Items]
Number of positions eliminated	55

Restructuring Charges - Restruc

Restructuring Charges - Restructuring Reserve (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Restructuring Reserve [Roll Forward]
Beginning balance			$ 448	$ 265	$ 265
Restructuring charges	$ 47	$ 15	69	235	589
Cash payments			(185)		(388)
Write-offs					(18)
Ending balance	30		30		448
2017 Restructuring Plan | Workforce Reduction Costs
Restructuring Reserve [Roll Forward]
Beginning balance			146	44	44
Restructuring charges			69		253
Cash payments			(185)		(151)
Write-offs					0
Ending balance	30		30		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		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		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 (Det

Related-Party Transactions (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2019USD ($)	Jun. 30, 2018USD ($)	Jun. 30, 2019USD ($)board_member	Jun. 30, 2018USD ($)	Dec. 31, 2018USD ($)
Adobe Systems | Chief Executive Officer
Related Party Transaction [Line Items]
Purchases from related party	$ 400,000	$ 600,000	$ 1,400,000	$ 2,300,000
Revenue from related parties	0	0	0	100,000
Due to related parties	0		0
Receivables from related party	0		0		$ 0
Cengage | Chief Executive Officer
Related Party Transaction [Line Items]
Revenue from related parties	400,000	100,000	1,600,000	2,000,000
Due to related parties					$ 100,000
Cengage | Board Of Directors Member
Related Party Transaction [Line Items]
Purchases from related party	1,500,000	1,400,000	$ 10,600,000	6,500,000
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	200,000	$ 800,000	600,000
Synack, Inc. | Board Of Directors Member
Related Party Transaction [Line Items]
Purchases from related party	$ 0	$ 0	$ 300,000	$ 0
Number of board members appointed to Board of Directors of related party | board_member			1

Uncategorized Items - chegg2019

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	$ (111,000)
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	(77,000)
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	(111,000)
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ (77,000)