Wayfair (W) 10-Q 3 Nov 20 2020 Q3 Quarterly report Financial data

Cover

Cover - shares	9 Months Ended
	Sep. 30, 2020	Oct. 27, 2020
Document Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2020
Document Transition Report	false
Entity File Number	001-36666
Entity Registrant Name	Wayfair Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	36-4791999
Entity Address, Address Line One	4 Copley Place
Entity Address, City or Town	Boston
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02116
City Area Code	617
Local Phone Number	532-6100
Title of 12(b) Security	Class A Common Stock, $0.001 par value per share
Trading Symbol	W
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Central Index Key	0001616707
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q3
Amendment Flag	false
Class A Common Stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		72,811,806
Class B Common Stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		26,636,234

CONSOLIDATED AND CONDENSED BALA

CONSOLIDATED AND CONDENSED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Current assets
Cash and cash equivalents	$ 2,442,939	$ 582,753
Short-term investments	113,985	404,252
Accounts receivable, net of allowance for credit losses of $26,884 and $22,774 at September 30, 2020 and December 31, 2019, respectively	109,652	99,720
Inventories	54,241	61,692
Prepaid expenses and other current assets	322,649	228,721
Total current assets	3,043,466	1,377,138
Operating lease right-of-use assets	802,369	763,400
Property and equipment, net	682,057	624,544
Goodwill and intangible assets, net	17,605	18,809
Long-term investments	0	155,690
Other noncurrent assets	12,943	13,467
Total assets	4,558,440	2,953,048
Current liabilities
Accounts payable	1,236,895	908,097
Accrued expenses	328,694	298,918
Unearned revenue	318,175	167,641
Other current liabilities	333,589	236,863
Total current liabilities	2,217,353	1,611,519
Long-term debt	2,862,135	1,456,195
Operating lease liabilities	867,711	822,602
Other liabilities	70,827	6,940
Total liabilities	6,018,026	3,897,256
Commitments and contingencies (Note 8)
Stockholders’ deficit:
Undesignated preferred stock, $0.001 par value per share: 10,000,000 shares authorized and none issued at September 30, 2020 and December 31, 2019	0	0
Additional paid-in capital	452,111	1,122,548
Accumulated deficit	(1,909,768)	(2,065,423)
Accumulated other comprehensive loss	(2,025)	(1,427)
Total stockholders’ deficit	(1,459,586)	(944,208)
Total liabilities and stockholders’ deficit	4,558,440	2,953,048
Class A common stock
Stockholders’ deficit:
Common stock	69	67
Class B common stock
Stockholders’ deficit:
Common stock	$ 27	$ 27

CONSOLIDATED AND CONDENSED BA_2

CONSOLIDATED AND CONDENSED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Accounts receivable allowance for credit losses	$ 26,884	$ 22,774
Undesignated preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Undesignated preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Undesignated preferred shares, shares issued (in shares)	0	0
Class A common stock
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	500,000,000	500,000,000
Common stock, shares issued (in shares)	68,959,957	66,642,611
Common stock, shares outstanding (in shares)	68,959,957	66,642,611
Class B common stock
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	164,000,000	164,000,000
Common stock, shares issued (in shares)	26,636,721	26,957,815
Common stock, shares outstanding (in shares)	26,636,721	26,957,815

CONSOLIDATED AND CONDENSED STAT

CONSOLIDATED AND CONDENSED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Income Statement [Abstract]
Net revenue	$ 3,839,570	$ 2,305,487	$ 10,474,305	$ 6,593,567
Cost of goods sold	2,692,142	1,765,566	7,426,724	5,023,590
Gross profit	1,147,428	539,921	3,047,581	1,569,977
Operating expenses:
Customer service and merchant fees	139,589	91,255	372,825	256,230
Advertising	344,025	281,846	1,037,562	784,981
Selling, operations, technology, general and administrative	441,960	426,529	1,377,410	1,153,286
Total operating expenses	925,574	799,630	2,787,797	2,194,497
Income (loss) from operations	221,854	(259,709)	259,784	(624,520)
Interest (expense), net	(36,315)	(14,432)	(87,472)	(33,922)
Other (expense) income, net	(13,584)	2,182	(10,720)	5,582
Income (loss) before income taxes	171,955	(271,959)	161,592	(652,860)
(Benefit) provision for income taxes, net	(1,211)	76	414	1,502
Net income (loss)	$ 173,166	$ (272,035)	$ 161,178	$ (654,362)
Basic earnings (loss) per share (in usd per share)	$ 1.82	$ (2.94)	$ 1.70	$ (7.13)
Diluted earnings (loss) per share (in usd per share)	$ 1.67	$ (2.94)	$ 1.64	$ (7.13)
Weighted-average number of shares of common stock outstanding used in computing per share amounts:
Basic (in shares)	95,373	92,540	94,767	91,820
Diluted (in shares)	109,200	92,540	98,021	91,820

CONSOLIDATED AND CONDENSED ST_2

CONSOLIDATED AND CONDENSED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 173,166	$ (272,035)	$ 161,178	$ (654,362)
Other comprehensive income (loss):
Foreign currency translation adjustments	(895)	(75)	(665)	129
Net unrealized (loss) gain on available-for-sale investments	(606)	(5)	67	195
Comprehensive income (loss)	$ 171,665	$ (272,115)	$ 160,580	$ (654,038)

CONSOLIDATED AND CONDENSED ST_3

CONSOLIDATED AND CONDENSED STATEMENTS OF STOCKHOLDERS' DEFICIT - USD ($) shares in Thousands, $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment	Class A and Class B Common Stock	Additional Paid-In Capital	Accumulated Deficit	Accumulated DeficitCumulative Effect, Period of Adoption, Adjustment	Accumulated Other Comprehensive Loss
Balance (in shares) at Dec. 31, 2018			90,748
Balance at Dec. 31, 2018	$ (330,721)	$ 1,850	$ 91	$ 753,657	$ (1,082,689)	$ 1,850	$ (1,780)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	(654,362)				(654,362)
Other comprehensive (loss) income	324						324
Exercise of options to purchase common stock (in shares)			28
Exercise of options to purchase common stock	90			90
Issuance of common stock upon vesting of RSUs (in shares)			2,109
Issuance of common stock upon vesting of RSUs	2		$ 2
Shares withheld related to net settlement of RSUs (in shares)			(11)
Shares withheld related to net settlement of RSUs	(1,510)			(1,510)
Equity-based compensation expense	171,332			171,332
Equity component of issuance of convertible notes and capped calls, net	130,566			130,566
Balance (in shares) at Sep. 30, 2019			92,874
Balance at Sep. 30, 2019	(682,429)		$ 93	1,054,135	(1,735,201)		(1,456)
Balance (in shares) at Jun. 30, 2019			92,098
Balance at Jun. 30, 2019	(605,357)		$ 93	859,092	(1,463,166)		(1,376)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	(272,035)				(272,035)
Other comprehensive (loss) income	(80)						(80)
Exercise of options to purchase common stock (in shares)			3
Exercise of options to purchase common stock	10			10
Issuance of common stock upon vesting of RSUs (in shares)			781
Issuance of common stock upon vesting of RSUs	0
Shares withheld related to net settlement of RSUs (in shares)			(8)
Shares withheld related to net settlement of RSUs	(1,086)			(1,086)
Equity-based compensation expense	65,553			65,553
Equity component of issuance of convertible notes and capped calls, net	130,566			130,566
Balance (in shares) at Sep. 30, 2019			92,874
Balance at Sep. 30, 2019	(682,429)		$ 93	1,054,135	(1,735,201)		(1,456)
Balance (in shares) at Dec. 31, 2019			93,600
Balance at Dec. 31, 2019	(944,208)	$ (5,523)	$ 94	1,122,548	(2,065,423)	$ (5,523)	(1,427)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	161,178				161,178
Other comprehensive (loss) income	(598)						(598)
Exercise of options to purchase common stock (in shares)			24
Exercise of options to purchase common stock	380			380
Issuance of common stock upon vesting of RSUs (in shares)			2,234
Issuance of common stock upon vesting of RSUs	2		$ 2
Equity-based compensation expense	208,740			208,740
Repurchase of common stock (in shares)			(844)
Repurchase of common stock	(280,236)		$ (1)	(280,235)
Shares issued upon conversion of convertible notes (Note 15) (in shares)			583
Shares issued upon conversion of convertible notes (Note 15)	151,420		$ 1	151,419
Reacquisition of equity component from repurchases and conversions of convertible notes, net of taxes (Note 15)	(829,004)			(829,004)
Equity component of issuance of convertible notes and capped calls, net	78,263			78,263
Balance (in shares) at Sep. 30, 2020			95,597
Balance at Sep. 30, 2020	(1,459,586)		$ 96	452,111	(1,909,768)		(2,025)
Balance (in shares) at Jun. 30, 2020			95,065
Balance at Jun. 30, 2020	(787,392)		$ 95	1,295,971	(2,082,934)		(524)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (loss) income	173,166				173,166
Other comprehensive (loss) income	(1,501)						(1,501)
Exercise of options to purchase common stock (in shares)			6
Exercise of options to purchase common stock	161			161
Issuance of common stock upon vesting of RSUs (in shares)			787
Issuance of common stock upon vesting of RSUs	1		$ 1
Equity-based compensation expense	74,425			74,425
Repurchase of common stock (in shares)			(844)
Repurchase of common stock	(280,236)		$ (1)	(280,235)
Shares issued upon conversion of convertible notes (Note 15) (in shares)			583
Shares issued upon conversion of convertible notes (Note 15)	151,420		$ 1	151,419
Reacquisition of equity component from repurchases and conversions of convertible notes, net of taxes (Note 15)	(829,004)			(829,004)
Equity component of issuance of convertible notes and capped calls, net	39,374			39,374
Balance (in shares) at Sep. 30, 2020			95,597
Balance at Sep. 30, 2020	$ (1,459,586)		$ 96	$ 452,111	$ (1,909,768)		$ (2,025)

CONSOLIDATED AND CONDENSED ST_4

CONSOLIDATED AND CONDENSED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Cash flows from operating activities:
Net income (loss)	$ 161,178	$ (654,362)
Adjustments used to reconcile net income (loss) to net cash used in operating activities
Depreciation and amortization	208,532	134,172
Equity-based compensation	197,199	162,014
Amortization of discount and issuance costs on convertible notes	78,225	40,737
Other non-cash adjustments	12,065	(1,659)
Changes in operating assets and liabilities:
Accounts receivable, net	(14,891)	(25,309)
Inventories	7,602	(22,716)
Prepaid expenses and other current assets	(93,055)	(29,648)
Accounts payable and accrued expenses	356,215	215,786
Unearned revenue and other liabilities	296,306	22,382
Other assets	612	(1,920)
Net cash provided by (used in) operating activities	1,209,988	(160,523)
Cash flows from investing activities:
Purchase of short- and long-term investments	(19,994)	0
Sale and maturities of short- and long-term investments	466,310	115,468
Purchase of property and equipment	(146,303)	(183,968)
Site and software development costs	(109,678)	(94,697)
Other investing activities, net	(124)	(15,977)
Net cash provided by (used in) investing activities	190,211	(179,174)
Cash flows from financing activities:
Proceeds from borrowings	200,000	0
Repayment of borrowings	(200,000)	0
Proceeds from issuance of convertible notes, net of issuance costs	2,027,758	935,146
Premiums paid for capped call confirmations	(255,024)	(145,728)
Payments to extinguish convertible debt	(1,040,349)	0
Repurchase of common stock	(280,236)	0
Other financing activities, net	380	(2,211)
Net cash provided by financing activities	452,529	787,207
Effect of exchange rate changes on cash and cash equivalents	7,458	(1,586)
Net increase in cash and cash equivalents	1,860,186	445,924
Cash and cash equivalents:
Beginning of period	582,753	849,461
End of period	2,442,939	1,295,385
Supplemental cash flow information:
Cash paid for interest on long-term debt	14,173	4,528
Issuance of common stock for conversion of convertible debt, net of taxes	45,447	0
Purchase of property and equipment included in accounts payable and accrued expenses and in other liabilities	$ 38,391	$ 34,028

Description of Business

Description of Business	9 Months Ended
	Sep. 30, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business	1. Description of Business Wayfair Inc. (the "Company") is one of the world's largest online destinations for the home. Through its e-commerce business model, the Company offers visually inspired browsing, compelling merchandising, easy product discovery and attractive prices for over eighteen million products from over 12,000 suppliers.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2020
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation The accompanying unaudited Consolidated and Condensed Financial Statements contained in this Quarterly Report on Form 10-Q are those of the Company and have been prepared in accordance with generally accepted accounting principles in the United States ("GAAP") and applicable rules and regulations of the U.S. Securities and Exchange Commission ("SEC") regarding interim financial reporting. Certain information and note disclosures normally included in the audited financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. As such, the information included in this Quarterly Report on Form 10-Q should be read in conjunction with the audited consolidated financial statements and accompanying notes included in our Annual Report on Form 10-K for the year ended December 31, 2019. The Consolidated and Condensed Balance Sheet as of December 31, 2019 included herein was derived from the audited financial statements as of that date, but does not include all disclosures including notes required by GAAP. The accompanying unaudited Consolidated and Condensed Financial Statements have been prepared on the same basis as the audited consolidated financial statements and, in the opinion of management, reflect all adjustments, consisting of normal recurring adjustments, that are necessary to present fairly the results of the interim periods presented. Interim results are not necessarily indicative of the results for the full year ended December 31, 2020 or future periods. The Company believes that other than the implementation of Accounting Standards Update (“ASU”) No. 2016-13, Financial Instruments – Credit Losses (Topic 326), Measurement of Credit Losses on Financial Instruments ("ASU 2016-13"), there have been no significant changes during the nine months ended September 30, 2020 to the items disclosed in Note 2, Summary of Significant Accounting Policies , included in Part II, Item 8, Financial Statements and Supplementary Data , of the Company’s Annual Report on Form 10-K for the year ended December 31, 2019. Principles of Consolidation The accompanying unaudited Consolidated and Condensed Financial Statements of Wayfair Inc. include its wholly-owned subsidiaries. All intercompany accounts and transactions have been eliminated. Use of Estimates The preparation of the unaudited Consolidated and Condensed Financial Statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, and disclosure of contingent assets and liabilities, at the date of the financial statements and the reported amounts of net revenues and expenses during the reporting period. Actual results could differ from those estimates. Earnings (Loss) per Share The Company follows the two-class method when computing earnings (loss) per share for its two issued classes of common stock - Class A and Class B. Basic earnings (loss) per share is computed using the weighted-average number of shares of common stock outstanding during the period. Diluted earnings (loss) per share is computed using the weighted-average number of shares of common stock outstanding during the period plus, if dilutive, stock awards, including stock options and restricted stock units, as determined under the treasury stock method, and convertible debt instruments, as determined under the if-converted method. In periods when we have a net loss, stock awards and convertible debt instruments are excluded from our calculations of earnings per share as their inclusion would have an antidilutive effect. Credit Impairment The Company adopted ASU No. 2016-13 on January 1, 2020 using the modified retrospective transition method. This ASU revises how entities account for credit losses for most financial assets and certain other instruments that are not measured at fair value through net income. As of January 1, 2020, the adoption of ASU 2016-13 Credit Losses , for additional detail. 18. Recent Accounting Pronouncements In August 2020, the FASB issued ASU No. 2020-06, Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging—Contracts in Entity’s Own Equity (Subtopic 815-40) (“ASU 2020-06”). This ASU simplifies the accounting for convertible instruments by removing the separation models for convertible debt with cash conversion features and convertible instruments with a beneficial conversion feature. Under ASU 2020-06, a convertible debt instrument with those features will generally be reported as a single liability at its amortized cost with no separate accounting for the embedded conversion features. We expect the elimination of these models will reduce reported interest expense and increase reported net income for the Company’s existing convertible instruments falling under the scope of those models before the adoption of ASU 2020-06. ASU 2020-06 requires the application of the if-converted method when calculating diluted earnings per share, eliminating the Company’s ability to use the treasury stock method when certain conditions are met. The ASU is effective for annual reporting periods beginning after December 15, 2021, with early adoption permitted no earlier than fiscal years

Investments and Fair Value Meas

Investments and Fair Value Measurements	9 Months Ended
	Sep. 30, 2020
Fair Value Disclosures [Abstract]
Investments and Fair Value Measurements	3. Investments and Fair Value Measurements Investments As of September 30, 2020 and December 31, 2019, the Company's investments consisted of corporate bonds and other government obligations priced at fair value. These investments were classified as available-for-sale and their estimated fair values were $114.0 million and $559.9 million, respectively. To the extent the amortized cost basis of the available-for-sale debt securities exceeds the fair value, management assesses the debt securities for credit loss, however management considers the risk of credit loss to be minimized by the Company's policy of investing in financial instruments issued by highly-rated financial institutions. When assessing the risk of credit loss, management considers factors such as the severity and the reason of the decline in value (i.e., any changes to the rating of the security by a rating agency or other adverse conditions specifically related to the security) and management's intended holding period and time horizon for selling. During the three and nine months ended September 30, 2020 and 2019, the Company did not recognize any credit losses related to its available-for-sale debt securities. Further, as of September 30, 2020 and December 31, 2019, the Company did not record an allowance for credit losses related to its available-for-sale debt securities. During the nine months ended September 30, 2020, the Company collected $161.3 million of proceeds from the sale of long-term investments and recognized a realized gain of $0.8 million. The Company did not recognize any realized gains or losses during the three months ended September 30, 2020 or during the three and nine months ended September 30, 2019. The following tables present details of the Company’s investments as of September 30, 2020 and December 31, 2019: September 30, 2020 Amortized Gross Gross Estimated (in thousands) Short-term: Investment securities $ 113,886 $ 99 $ — $ 113,985 Total $ 113,886 $ 99 $ — $ 113,985 December 31, 2019 Amortized Gross Unrealized Gains Gross Estimated (in thousands) Short-term: Investment securities $ 404,294 $ 20 $ (62) $ 404,252 Long-term: Investment securities 155,616 92 (18) 155,690 Total $ 559,910 $ 112 $ (80) $ 559,942 Fair Value Measurements The Company's financial assets and liabilities are measured at fair value, which is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date (exit price). The three levels of inputs used to measure fair value are as follows: ▪ Level 1—Unadjusted quoted prices in active markets for identical assets or liabilities ▪ Level 2—Unadjusted quoted prices in active markets for similar assets or liabilities, unadjusted quoted prices for identical or similar assets or liabilities in markets that are not active, or inputs other than quoted prices that are observable or can be corroborated by observable market data for substantially the full-term of the asset or liability ▪ Level 3—Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the asset or liability This hierarchy requires the Company to use observable market data, when available, and to minimize the use of unobservable inputs when determining fair value. The Company measures its cash equivalents and short- and long-term investments at fair value. The Company classifies its cash equivalents and certificates of deposits within Level 1 because the Company values these investments using quoted market prices. The fair value of the Company's Level 1 financial assets is based on quoted market prices of the identical underlying security. The Company classifies short- and long-term investments within Level 2 because unadjusted quoted prices for identical or similar assets in markets are not active. The following tables set forth the fair value of the Company’s financial assets measured at fair value on a recurring basis as of September 30, 2020 and December 31, 2019 based on the three-tier value hierarchy: September 30, 2020 Level 1 Level 2 Level 3 Total (in thousands) Cash and cash equivalents: Cash $ 538,767 $ — $ — $ 538,767 Cash equivalents 1,904,172 — — 1,904,172 Total cash and cash equivalents 2,442,939 — — 2,442,939 Short-term investments: Investment securities — 113,985 — 113,985 Other non-current assets: Certificate of deposit 5,200 — — 5,200 Total $ 2,448,139 $ 113,985 $ — $ 2,562,124 December 31, 2019 Level 1 Level 2 Level 3 Total (in thousands) Cash and cash equivalents: Cash $ 308,521 $ — $ — $ 308,521 Cash equivalents 274,232 — — 274,232 Total cash and cash equivalents 582,753 — — 582,753 Short-term investments: Investment securities — 404,252 — 404,252 Other non-current assets: Certificate of deposit 5,076 — — 5,076 Long-term investments: Investment securities — 155,690 — 155,690 Total $ 587,829 $ 559,942 $ — $ 1,147,771

Credit Losses

Credit Losses	9 Months Ended
	Sep. 30, 2020
Credit Loss [Abstract]
Credit Losses	4. Credit Losses Accounts receivable are stated net of the allowance for credit losses, which are recorded based on historical losses as well as management's expectation of future collections. Uncollectible amounts are written off against the allowance after all collection efforts have been exhausted. The Company's exposure to credit loss is minimized through fraud assessments performed prior to customer checkout and the Company's policy of monitoring the creditworthiness of its customers to which it grants credit terms in the normal course of business. Further, management notes credit risk is mitigated as approximately 99% of the net revenue recognized for the three and nine months ended September 30, 2020 was collected in advance of recognition. As of September 30, 2020, the Company reported $109.7 million of accounts receivable, net of allowance for credit losses of $26.9 million. Other than the adjustment related to the adoption of ASU 2016-13, as discussed in Note 2, Summary of Significant Accounting Policies

Intangible Assets and Goodwill

Intangible Assets and Goodwill	9 Months Ended
	Sep. 30, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible Assets and Goodwill	5. Intangible Assets and Goodwill As of September 30, 2020 and December 31, 2019, the Company had $17.2 million and $18.4 million of intangible assets, respectively. Amortization expense related to intangible assets was $0.4 million and $0.1 million for the three months ended September 30, 2020 and 2019, respectively, and $1.2 million and $0.4 million for the nine months ended September 30, 2020 and 2019, respectively.

Property and Equipment, net

Property and Equipment, net	9 Months Ended
	Sep. 30, 2020
Property, Plant and Equipment [Abstract]
Property and Equipment, net	6. Property and Equipment, net The following table summarizes property and equipment, net as of September 30, 2020 and December 31, 2019: September 30, December 31, (in thousands) Furniture and computer equipment $ 554,489 $ 509,120 Site and software development costs 397,027 297,252 Leasehold improvements 341,345 228,514 Construction in progress 23,667 45,503 1,316,528 1,080,389 Less accumulated depreciation and amortization (634,471) (455,845) Property and equipment, net $ 682,057 $ 624,544 Property and equipment depreciation and amortization expense was $72.2 million and $50.1 million for the three months ended September 30, 2020 and 2019, respectively, and $207.3 million and $133.8 million for the nine months ended September 30, 2020 and 2019, respectively.

Leases

Leases	9 Months Ended
	Sep. 30, 2020
Leases [Abstract]
Leases	7. Leases The Company has lease arrangements for warehouse, fulfillment center, office, and data center spaces. These leases expire at various dates through 2034. Operating lease expense was $38.6 million and $31.8 million in the three months ended September 30, 2020 and 2019, respectively, and $118.8 million and $86.8 million for the nine months ended September 30, 2020 and 2019, respectively. The following table presents supplemental cash flow information related to leases: Nine months ended September 30, 2020 Nine months ended September 30, 2019 (in thousands) Cash payments included in operating cash flows from lease arrangements $ 105,416 $ 77,687 Right-of-use assets obtained in exchange for lease obligations $ 110,210 $ 281,006 The following table presents supplemental balance sheet information related to leases: September 30, 2020 December 31, 2019 Additional lease information Weighted average remaining lease term 8 years 10 years Weighted average discount rate 6.5 % 6.7 % The following table presents future minimum lease payments under non-cancellable leases as of September 30, 2020: Amount (in thousands) 2020 (excluding the nine months ended September 30, 2020) $ 33,793 2021 161,998 2022 162,800 2023 157,581 2024 155,062 Thereafter 602,837 Total future minimum lease payments 1,274,071 Less: Imputed interest (303,994) Total $ 970,077 The following table presents total operating leases as of September 30, 2020 and December 31, 2019: September 30, December 31, (in thousands) Balance sheet line item Other current liabilities $ 102,366 $ 91,104 Operating lease liabilities 867,711 822,602 Total operating leases $ 970,077 $ 913,706 As of September 30, 2020, the Company has entered into $149.4 million of additional operating leases, primarily related to build-to-suit warehouse leases that have not yet commenced. As the Company does not control the underlying assets during the construction period, the Company is not considered the owner of the construction projects for accounting purposes. These operating leases will commence between 2020 and 2021 with lease terms of 2 to 15 years.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2020
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	8. Commitments and Contingencies Letters of Credit The Company has issued letters of credit, primarily as security for certain lease agreements, for approximately $54.9 million and $46.7 million, as of September 30, 2020 and December 31, 2019, respectively. Legal Matters From time to time the Company is involved in claims that arise during the ordinary course of business. Although the results of litigation and claims cannot be predicted with certainty, the Company does not currently believe that the outcome of any of these legal matters will have a material adverse effect on the Company's results of operation or financial condition. Regardless of the outcome, litigation can be costly and time consuming, as it can divert management's attention from important business matters and initiatives, negatively impacting the Company's overall operations. In addition, the Company may also find itself at greater risk to outside party claims as it increases its operations in jurisdictions where the laws with respect to the potential liability of online retailers are uncertain, unfavorable, or unclear. On January 10, 2019 and January 16, 2019, putative securities class action complaints were filed against the Company and three of its officers in the U.S. District Court for the District of Massachusetts. The two complaints alleged violations of Sections 10(b) and 20(a) of the Securities Exchange Act of 1934, as amended, relating to certain prior disclosures of the

Equity-Based Compensation

Equity-Based Compensation	9 Months Ended
	Sep. 30, 2020
Share-based Payment Arrangement [Abstract]
Equity-Based Compensation	9. Equity-Based Compensation The board of directors of the Company (the "Board") adopted the 2014 Incentive Award Plan ("2014 Plan") to grant cash and equity incentive awards to eligible participants in order to attract, motivate and retain talent. The 2014 Plan is administered by the Board with respect to awards to non-employee directors and by the compensation committee of the Board with respect to other participants and provides for the issuance of stock options, stock appreciation rights ("SARs"), restricted stock, restricted stock units ("RSUs"), performance shares, stock payments, cash payments, dividend awards and other incentives. Prior to the adoption of the 2014 Plan, Wayfair LLC issued certain equity awards pursuant to the Wayfair LLC Amended and Restated Common Unit Plan (the "2010 Plan"), which was administered by the board of directors of Wayfair LLC. Awards issued under the 2010 Plan that remain outstanding currently represent Class A or Class B common stock of the Company. For awards granted pursuant to the 2014 Plan, 8,603,066 shares of Class A common stock were initially available for issuance. The 2014 Plan also contains an evergreen provision whereby the shares available for future grant are increased on the first day of each calendar year beginning January 1, 2016 and ending on and including January 1, 2024. As of January 1, 2020, 5,111,305 shares of Class A common stock were available for future grant under the 2014 Plan. Shares or RSUs forfeited, withheld for minimum statutory tax obligations, and unexercised stock option lapses from the 2010 and 2014 Plans are available for future grant under the 2014 Plan. The following table presents activity relating to stock options for the nine months ended September 30, 2020: Shares Weighted-Average Exercise Price Weighted-Average Remaining Contractual Term (Years) Outstanding at December 31, 2019 43,606 $ 3.00 1.5 Options exercised (23,660) $ 3.02 Outstanding and exercisable at September 30, 2020 19,946 $ 2.98 0.7 The intrinsic value of stock options exercised was $4.4 million and $4.2 million for the nine months ended September 30, 2020 and 2019, respectively. The aggregate intrinsic value of stock options outstanding and currently exercisable is $5.7 million as of September 30, 2020. All stock options were fully vested at September 30, 2020. The following table presents activity relating to RSUs for the nine months ended September 30, 2020: Shares Weighted- Outstanding at December 31, 2019 8,112,736 $ 95.69 RSUs granted 1,688,442 $ 171.72 RSUs vested (2,233,708) $ 95.30 RSUs forfeited/canceled (1,343,119) $ 103.73 Outstanding as of September 30, 2020 6,224,351 $ 115.27 The intrinsic value of RSUs vested was $342.9 million and $290.5 million for the nine mon ths ended September 30, 2020 and 2019 , respectively. The aggregate intrinsic value of RSUs unvested is $1.8 billion as of September 30, 2020. Unrecognized equity-based compensation expense related to outstanding RSUs is $649.7 million with a weighted average remaining ve sting term of 1.2 years at September 30, 2020.

Unearned Revenue

Unearned Revenue	9 Months Ended
	Sep. 30, 2020
Revenue from Contract with Customer [Abstract]
Unearned Revenue	10. Unearned Revenue The Company has three types of contractual liabilities: (i) cash collections from its customers prior to delivery of products purchased, which are initially recorded in unearned revenue, and are recognized as net revenue when the products are delivered, (ii) unredeemed gift cards and site and store credits, which are initially recorded in unearned revenue, and are recognized in the period they are redeemed, and (iii) membership rewards redeemable for future purchases, which are earned by customers on purchases made with the Company's Wayfair branded, private label credit card, and are initially recorded in other current liabilities, and are recognized as net revenue when redeemed. The portion of gift cards and site and store credits not expected to be redeemed ("breakage") are recognized as net revenue based on historical redemption patterns, which is substantially within twenty-four months from the date of issuance, to the extent there is no requirement for remitting balances to governmental agencies. Contractual liabilities included in unearned revenue and other current liabilities in the Consolidated and Condensed Balance Sheet were $318.2 million and $5.3 million at September 30, 2020 and $167.6 million and $4.6 million at December 31, 2019, respectively. During the nine months ended September 30, 2020, the Company recognized $139.7 million and $2.8 million of net revenue that was included in unearned revenue and other current liabilities, respectively, at December 31, 2019. Net revenue from contracts with customers is disaggregated by geographic region because this manner of disaggregation best depicts how the nature, amount, timing, and uncertainty of net revenue and cash flows are affected by economic factors. Refer to Note 11, Segment and Geographic Information , for additional detail.

Segment and Geographic Informat

Segment and Geographic Information	9 Months Ended
	Sep. 30, 2020
Segment Reporting [Abstract]
Segment and Geographic Information	11. Segment and Geographic Information Operating segments are defined as components of an enterprise for which separate financial information is available that is evaluated on a regular basis by the Chief Operating Decision Maker ("CODM") in deciding how to allocate resources to an individual segment and in assessing performance. The Company’s CODM is its chief executive officer. The Company's operating and reportable segments are the U.S. and International. These segments reflect the way the CODM allocates resources and evaluates financial performance, which is based upon each segment's Adjusted EBITDA. Adjusted EBITDA is defined as net income (loss) before depreciation and amortization, equity-based compensation and related taxes, interest (expense), net, other (expense) income, net, (benefit) provision for income taxes, net, non-recurring items, and other items not indicative of our ongoing operating performance. These charges are excluded from evaluation of segment performance because it facilitates reportable segment performance comparisons on a period-to-period basis as these costs may vary independent of business performance. The Company allocates certain operating expenses to the operating and reportable segments, including customer service and merchant fees and selling, operations, technology, general and administrative based on the usage and relative contribution provided to the segments. It excludes from the allocations certain operating expense lines, including depreciation and amortization, equity-based compensation and related taxes, as well as interest (expense), net, other (expense) income, net, and (benefit) provision for income taxes, net. There are no net revenue transactions between the Company's reportable segments. U.S. The U.S. segment primarily consists of amounts earned through product sales through the Company's family of sites in the U.S. The U.S. net revenue for the three and nine months ended September 30, 2019 includes $5.8 million and $30.9 million, respectively of net revenue previously classified as other net revenue International The International segment primarily consists of amounts earned through product sales through the Company's international sites. Net revenue from external customers for each group of similar products and services are not reported to the CODM. Separate identification of this information for purposes of segment disclosure is impractical, as it is not readily available and the cost to develop it would be excessive. No individual country outside of the U.S. provided greater than 10% of consolidated net revenue. The following tables present net revenues and Adjusted EBITDA attributable to the Company's reportable segments for the periods presented: Three months ended September 30, Nine months ended September 30, 2020 2019 2020 2019 (in thousands) U.S. net revenue $ 3,274,872 $ 1,966,654 $ 8,901,559 $ 5,624,870 International net revenue 564,698 338,833 1,572,746 968,697 Total net revenue $ 3,839,570 $ 2,305,487 $ 10,474,305 $ 6,593,567 Three months ended September 30, Nine months ended September 30, 2020 2019 2020 2019 (in thousands) Adjusted EBITDA: U.S. $ 377,007 $ (62,878) $ 766,486 $ (91,002) International (5,895) (81,306) (82,838) (225,383) Total reportable segments Adjusted EBITDA 371,112 (144,184) 683,648 (316,385) Less: reconciling items (1) (197,946) (127,851) (522,470) (337,977) Net income (loss) $ 173,166 $ (272,035) $ 161,178 $ (654,362) (1) The following adjustments are made to reconcile total reportable segments Adjusted EBITDA to consolidated net income (loss): Three months ended September 30, Nine months ended September 30, 2020 2019 2020 2019 (in thousands) Depreciation and amortization $ 72,575 $ 50,250 $ 208,532 $ 134,172 Equity-based compensation and related taxes 76,683 65,275 211,376 173,963 Interest expense, net 36,315 14,432 87,472 33,922 Other expense (income), net 13,584 (2,182) 10,720 (5,582) (Benefit) provision for income taxes, net (1,211) 76 414 1,502 Other (1) — — 3,956 — Total reconciling items $ 197,946 $ 127,851 $ 522,470 $ 337,977

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2020
Income Tax Disclosure [Abstract]
Income Taxes	12. Income Taxes The (benefit) provision for income taxes, net was $(1.2) million and $0.1 million for the three months ended September 30, 2020 and 2019, respectively, and $0.4 million and $1.5 million for the nine months ended September 30, 2020 and 2019, respectively. The (benefit) provision for income taxes, net recorded in the three and nine months ended September 30, 2020 is primarily related to income earned in the U.S. and certain foreign jurisdictions and U.S. state income taxes, offset by a discrete tax benefit related to excess tax benefits on equity awards for U.S. employees. The (benefit) provision for income taxes, net recorded in the three and nine months ended September 30, 2019 is primarily related to income earned in certain foreign jurisdictions and U.S. state income taxes. Deferred income taxes reflect the impact of temporary differences between the amounts of assets and liabilities for financial reporting purposes and such amounts as measured by tax laws. The Company has deferred tax assets related to its net operating loss carryforwards accumulated since the fourth quarter of 2014 and related to net operating loss carryforwards of certain of its foreign subsidiaries. A valuation allowance against net deferred tax assets is required if, based upon the available evidence, it is more likely than not that some or all of the deferred tax assets will not be realized. The Company reassesses the

Stockholders' Deficit

Stockholders' Deficit	9 Months Ended
	Sep. 30, 2020
Equity [Abstract]
Stockholders' Deficit	13. Stockholders’ Deficit Preferred Stock The Company authorized 10,000,000 shares of undesignated preferred stock, $0.001 par value per share, for future issuance. As of September 30, 2020, the Company had no shares of undesignated preferred stock issued or outstanding. Common Stock The Company authorized 500,000,000 shares of Class A common stock, $0.001 par value per share, and 164,000,000 shares of Class B common stock, $0.001 par value per share, of which 68,959,957 and 66,642,611 shares of Class A common stock and 26,636,721 and 26,957,815 shares of Class B common stock were outstanding as of September 30, 2020 and December 31, 2019, respectively. The rights of the holders of Class A common stock and Class B common stock are identical, except with respect to voting and conversion rights. Each share of Class A common stock is entitled to one vote per share and each share of Class B common stock is entitled to ten votes per share. Each share of Class B common stock may be converted into one share of Class A common stock at the option of its holder and will be automatically converted into one share of Class A common stock upon transfer thereof, subject to certain exceptions. In addition, upon the date on which the outstanding shares of Class B common stock represent less than 10% of the aggregate number of shares of the then outstanding Class A common stock and Class B common stock, or in the event of the affirmative vote or written consent of holders of at least 66 2/3% of the outstanding shares of Class B common stock, all outstanding shares of Class B common stock shall convert automatically into Class A common stock. Subject to preferences that may apply to any shares of preferred stock outstanding at the time, the holders of common stock are entitled to receive dividends out of funds legally available if the Board, in its discretion, determines to issue dividends and then only at the times and in the amounts that the Board may determine. Since the Company's initial public offering through September 30, 2020, 55,401,693 shares of Class B common stock were converted to Class A common stock. Stock Repurchase Program On August 21, 2020, the Board authorized the repurchase of up to $700 million of the Company’s Class A common stock (the “2020 Repurchase Program”). The 2020 Repurchase Program replaced the Company’s previous $200 million stock repurchase authorization approved by the Board in 2018 (the “2018 Repurchase Program”), which was terminated simultaneously. During the three and nine months ended September 30, 2020, the Company repurchased $280.2 million through the stock repurchase programs at an average price of $331.65 per share of Class A common stock. During the three and nine months ended September 30, 2019, the Company did not repurchase any shares of common stock.

Credit Agreement

Credit Agreement	9 Months Ended
	Sep. 30, 2020
Debt Disclosure [Abstract]
Credit Agreement	14. Credit Agreement The Company has a credit agreement with certain lenders, which currently provides for a $200 million senior secured revolving credit facility maturing on February 21, 2022 (the “Revolver”). The Revolver contains affirmative and negative covenants customarily applicable to senior secured credit facilities, and also requires the Company to maintain certain levels of Free Cash Flow (as defined in the credit agreement). On August 21, 2020, in connection with the 2020 Repurchase Program, the Company amended the credit agreement for the Revolver to increase the Company’s stock repurchase basket in the negative covenant for restricted payments. The Company also increased the revolving loan commitment amount to $200 million on October 30, 2020 through an incremental commitment joinder. In the nine months ended September 30, 2020, the Company borrowed under the Revolver. All borrowings were repaid as of September 30, 2020. As a result, there were no amounts outstanding on the Revolver as of September 30, 2020. 15. Convertible Debt 2017 Notes and Capped Call Transactions On September 15, 2017, the Company issued $431.25 million in aggregate principal amount of 0.375% Convertible Senior Notes due 2022 (the "2017 Notes"), which includes the exercise in full of a $56.25 million over-allotment option, to certain financial institutions as the initial purchasers of the 2017 Notes (the "2017 Initial Purchasers"). On September 11, 2017, in connection with the pricing of the 2017 Notes, the Company entered into privately negotiated capped call transactions (the "2017 Base Capped Call Transactions") with two of the 2017 Initial Purchasers and certain other financial institutions (the "2017 Option Counterparties") and, in connection with the exercise in full of the over-allotment option by the 2017 Initial Purchasers, on September 14, 2017, entered into additional capped call transactions (such additional capped call transactions, the "2017 Additional Capped Call Transactions” and, together with the 2017 Base Capped Call Transactions, the "2017 Capped Call Transactions") with the 2017 Option Counterparties. Collectively, the 2017 Capped Call Transactions covered, initially, the number of shares of the Company’s Class A common stock underlying the 2017 Notes, subject to anti-dilution adjustments substantially similar to those applicable to the 2017 Notes. The 2017 Notes were issued pursuant to an indenture, dated September 15, 2017 (the "2017 Indenture"), between the Company and U.S. Bank National Association, as trustee. The Company pays interest on the 2017 Notes semiannually in arrears at a rate of 0.375% per annum on March 1 and September 1 of each year. The 2017 Notes are convertible based upon an initial conversion rate of 9.6100 shares of the Company’s Class A common stock per $1,000 principal amount of 2017 Notes (equivalent to a conversion price of approximately $104.06 per share of the Company’s Class A common stock). The conversion rate will be subject to adjustment upon the occurrence of certain specified events, including certain distributions and dividends to all or substantially all of the holders of the Company’s Class A common stock, but will not be adjusted for accrued and unpaid interest. The Company will settle any conversions of the 2017 Notes in cash, shares of the Company’s Class A common stock or a combination thereof, with the form of consideration determined at the Company’s election. The 2017 Notes will mature on September 1, 2022, unless earlier purchased, redeemed or converted. Prior to June 1, 2022, holders may convert all or a portion of their 2017 Notes only under the following circumstances: (1) during any calendar quarter (and only during such calendar quarter), if the last reported sale price of the Company’s Class A 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 conversion price on each applicable trading day; (2) during the 5 business day period after any 10 consecutive trading day period (the "2017 Notes measurement period") in which the trading price per $1,000 principal amount of 2017 Notes for each trading day of the 2017 Notes measurement period was less than 98% of the product of the last reported sale price of the Company’s Class A common stock and the conversion rate on each such trading day; (3) with respect to any 2017 Notes called for redemption by the Company, at any time prior to the close of business on the second scheduled trading day immediately preceding the redemption date; or (4) upon the occurrence of specified corporate events. On and after June 1, 2022 until the close of business on the second scheduled trading day immediately preceding the maturity date, holders may convert their 2017 Notes at any time, regardless of the foregoing circumstances. Holders of 2017 Notes who convert their 2017 Notes in connection with a notice of a redemption or a make-whole fundamental change (each as defined in the 2017 Indenture) may be entitled to a premium in the form of an increase in the conversion rate of the 2017 Notes. On November 15, 2018, the Company amended and restated the 2017 Capped Call Transactions (the "Restated 2017 Capped Call Transactions") with each of the 2017 Option Counterparties in order to, among other things, provide that the options underlying the Restated 2017 Capped Call Transactions can, at the Company’s option, remain outstanding until September 1, 2022, which is the maturity date for the 2017 Notes, even if all or a portion of the 2017 Notes are converted, repurchased or redeemed prior to such date. The Company could not redeem the 2017 Notes prior to September 8, 2020. On or after September 8, 2020, the Company may redeem for cash all or part of the 2017 Notes if the last reported sale price of the Company’s Class A common stock equals or exceeds 130% of the conversion price then in effect for at least 20 trading days (whether or not consecutive), including at least one of the five trading days immediately preceding the date on which the Company provides notice of redemption, during any 30 consecutive trading days ending on, and including the trading day immediately preceding the date on which the Company provides notice of the redemption. The redemption price will be 100% of the principal amount of the 2017 Notes to be redeemed, plus accrued and unpaid interest, if any. Upon the occurrence of a fundamental change (as defined in the 2017 Indenture), holders may require the Company to repurchase all or a portion of their 2017 Notes for cash at a price equal to 100% of the principal amount of the 2017 Notes to be repurchased plus any accrued but unpaid interest to, but excluding, the fundamental change repurchase date. The 2017 Indenture contains customary terms and covenants, including that upon certain events of default occurring and continuing, either the Trustee or the holders of not less than 25% in aggregate principal amount of the 2017 Notes then outstanding may declare the entire principal amount of all the 2017 Notes plus accrued interest, if any, to be immediately due and payable. 2018 Notes and Capped Call Transactions In November 2018, the Company issued $575.0 million in aggregate principal amount of 1.125% Convertible Senior Notes due 2024 (the "2018 Notes"), which includes the exercise in full of a $75.0 million option granted to the initial purchasers, to certain financial institutions as the initial purchasers of the 2018 Notes (the "2018 Initial Purchasers"). The issuance of $500.0 million of 2018 Notes closed on November 19, 2018 and the additional $75.0 million of additional 2018 Notes, which were issued pursuant to the exercise of the 2018 Initial Purchasers' option to purchase such additional 2018 Notes, closed on November 29, 2018. On November 14, 2018, in connection with the pricing of the 2018 Notes, the Company entered into privately negotiated capped call transactions (the "2018 Base Capped Call Transactions") with one of the 2018 Initial Purchasers and certain other financial institutions (the "2018 Option Counterparties") and, in connection with the exercise in full of the 2018 Initial Purchasers' option to purchase such additional 2018 Notes, on November 27, 2018, entered into additional capped call transactions (such additional capped call transactions, the "2018 Additional Capped Call Transactions" and, together with the 2018 Base Capped Call Transactions, the "2018 Capped Call Transactions") with the 2018 Option Counterparties. Collectively, the 2018 Capped Call Transactions cover, initially, the number of shares of the Company’s Class A common stock underlying the 2018 Notes, subject to anti-dilution adjustments substantially similar to those applicable to the 2018 Notes. The 2018 Notes were issued pursuant to an indenture, dated November 19, 2018 (the "2018 Indenture"), between the Company and U.S. Bank National Association, as trustee. The Company will pay interest on the 2018 Notes semiannually in arrears at a rate of 1.125% per annum on May 1 and November 1 of each year commencing on May 1, 2019. The 2018 Notes are convertible based upon an initial conversion rate of 8.5910 shares of the Company’s Class A common stock per $1,000 principal amount of 2018 Notes (equivalent to a conversion price of approximately $116.40 per share of the Company’s Class A common stock). The conversion rate will be subject to adjustment upon the occurrence of certain specified events, including certain distributions and dividends to all or substantially all of the holders of the Company’s Class A common stock, but will not be adjusted for accrued and unpaid interest. The Company will settle any conversions of the 2018 Notes in cash, shares of the Company’s Class A common stock or a combination thereof, with the form of consideration determined at the Company’s election. The 2018 Notes will mature on November 1, 2024, unless earlier purchased, redeemed or converted. Prior to August 1, 2024, holders may convert all or a portion of their 2018 Notes only under the following circumstances: (1) during any calendar quarter (and only during such calendar quarter), if the last reported sale price of the Company’s Class A 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 conversion price on each applicable trading day; (2) during the five ten The Company may not redeem the 2018 Notes prior to May 8, 2022. On or after May 8, 2022, the Company may redeem for cash all or part of the 2018 Notes if the last reported sale price of the Company’s Class A common stock equals or exceeds 130% of the conversion price then in effect for at least 20 trading days (whether or not consecutive), including at least one of the five trading days immediately preceding the date on which the Company provides notice of redemption, during any 30 consecutive trading days ending on, and including the trading day immediately preceding the date on which the Company provides notice of the redemption. The redemption price will be 100% of the principal amount of the 2018 Notes to be redeemed, plus accrued and unpaid interest, if any. Upon the occurrence of a fundamental change (as defined in the 2018 Indenture), holders may require the Company to repurchase all or a portion of their 2018 Notes for cash at a price equal to 100% of the principal amount of the 2018 Notes to be repurchased plus any accrued but unpaid interest to, but excluding, the fundamental change repurchase date. The 2018 Indenture contains customary terms and covenants, including that upon certain events of default occurring and continuing, either the Trustee or the holders of not less than 25% in aggregate principal amount of the 2018 Notes then outstanding may declare the entire principal amount of all the 2018 Notes plus accrued interest, if any, to be immediately due and payable. 2019 Notes and Capped Call Transactions On August 19, 2019, the Company issued $948.75 million in aggregate principal amount of 1.00% Convertible Senior Notes due 2026 (the "2019 Notes"), which includes the exercise in full of a $123.75 million option granted to the initial purchasers, to certain financial institutions as the initial purchasers of the 2019 Notes (the "2019 Initial Purchasers"). On August 14, 2019, in connection with the pricing of the 2019 Notes, the Company entered into privately negotiated capped call transactions (the "2019 Base Capped Call Transactions") with certain of the 2019 Initial Purchasers or their affiliates and another financial institution (the "2019 Option Counterparties") and, in connection with the exercise in full of the 2019 Initial Purchasers' option to purchase such additional 2019 Notes, on August 16, 2019, entered into additional capped call transactions (such additional capped call transactions, the "2019 Additional Capped Call Transactions" and, together with the 2019 Base Capped Call Transactions, the "2019 Capped Call Transactions") with the 2019 Option Counterparties. Collectively, the 2019 Capped Call Transactions cover, initially, the number of shares of the Company’s Class A common stock underlying the 2019 Notes, subject to anti-dilution adjustments substantially similar to those applicable to the 2019 Notes. The 2019 Notes were issued pursuant to an indenture, dated August 19, 2019 (the "2019 Indenture"), between the Company and U.S. Bank National Association, as trustee. The Company will pay interest on the 2019 Notes semiannually in arrears at a rate of 1.00% per annum on February 15 and August 15 of each year commencing on February 15, 2020. The 2019 Notes are convertible based upon an initial conversion rate of 6.7349 shares of the Company’s Class A common stock per $1,000 principal amount of 2019 Notes (equivalent to a conversion price of approximately $148.48 per share of the Company’s Class A common stock). The conversion rate will be subject to adjustment upon the occurrence of certain specified events, including certain distributions and dividends to all or substantially all of the holders of the Company’s Class A common stock, but will not be adjusted for accrued and unpaid interest. The Company will settle any conversions of the 2019 Notes in cash, shares of the Company’s Class A common stock or a combination thereof, with the form of consideration determined at the Company’s election. The 2019 Notes will mature on August 15, 2026, unless earlier purchased, redeemed or converted. Prior to May 15, 2026, holders may convert all or a portion of their 2019 Notes only under the following circumstances: (1) during any calendar quarter commencing after the calendar quarter ending on December 31, 2019 (and only during such calendar quarter), if the last reported sale price of the Company’s Class A 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 conversion price on each applicable trading day; (2) during the five ten The Company may not redeem the 2019 Notes prior to August 20, 2023. On or after August 20, 2023, the Company may redeem for cash all or part of the 2019 Notes if the last reported sale price of the Company’s Class A common stock equals or exceeds 130% of the conversion price then in effect for at least 20 trading days (whether or not consecutive), including at least one of the five trading days immediately preceding the date on which the Company provides notice of redemption, during any 30 consecutive trading days ending on, and including the trading day immediately preceding the date on which the Company provides notice of the redemption. The redemption price will be 100% of the principal amount of the 2019 Notes to be redeemed, plus accrued and unpaid interest, if any. Upon the occurrence of a fundamental change (as defined in the 2019 Indenture), holders may require the Company to repurchase all or a portion of their 2019 Notes for cash at a price equal to 100% of the principal amount of the 2019 Notes to be repurchased plus any accrued but unpaid interest to, but excluding, the fundamental change repurchase date. The 2019 Indenture contains customary terms and covenants, including that upon certain events of default occurring and continuing, either the Trustee or the holders of not less than 25% in aggregate principal amount of the 2019 Notes then outstanding may declare the entire principal amount of all the 2019 Notes plus accrued interest, if any, to be immediately due and payable. 2020 Notes and Capped Call Transactions On August 14, 2020, the Company issued $1.518 billion in aggregate principal amount of 0.625% Convertible Senior Notes due 2025 (the “2020 Notes”, and together with the 2017 Notes, the 2018 Notes and the 2019 Notes, the “Non-Accreting Notes”), which includes the exercise in full of a $198.0 million option granted to the initial purchasers, to certain financial institutions as the initial purchasers of the 2020 Notes (the “2020 Initial Purchasers”). On August 11, 2020, in connection with the pricing of the 2020 Notes, the Company entered into privately negotiated capped call transactions (the “2020 Base Capped Call Transactions”) with certain of the 2020 Initial Purchasers or their respective affiliates and certain other financial institutions (the “2020 Option Counterparties”) and, in connection with the exercise in full of the 2020 Initial Purchasers’ option to purchase such additional 2020 Notes, on August 12, 2020, entered into additional capped call transactions (such additional capped call transactions, the “2020 Additional Capped Call Transactions” and together with the 2020 Base Capped Call Transactions, the “2020 Capped Call Transactions”) with the 2020 Option Counterparties. Collectively, the 2020 Capped Call Transactions cover, initially, the number of shares of the Company’s Class A common stock underlying the 2020 Notes, subject to anti-dilution adjustments substantially similar to those applicable to the 2020 Notes. The 2020 Notes were issued pursuant to an indenture, dated August 14, 2020 (the "2020 Indenture"), between the Company and U.S. Bank National Association, as trustee. The Company will pay interest on the 2020 Notes semiannually in arrears at a rate of 0.625% per annum on April 1 and October 1 of each year commencing on April 1, 2021. The 2020 Notes are convertible based upon an initial conversion rate of 2.3972 shares of the Company’s Class A common stock per $1,000 principal amount of 2020 Notes (equivalent to a conversion price of approximately $417.15 per share of the Company’s Class A common stock). The conversion rate will be subject to adjustment upon the occurrence of certain specified events, including certain distributions and dividends to all or substantially all of the holders of the Company’s Class A common stock, but will not be adjusted for accrued and unpaid interest. The Company will settle any conversions of the 2020 Notes in cash, shares of the Company’s Class A common stock or a combination thereof, with the form of consideration determined at the Company’s election. The 2020 Notes will mature on October 1, 2025, unless earlier purchased, redeemed or converted. Prior to July 1, 2025, holders may convert all or a portion of their 2020 Notes only under the following circumstances: (1) during any calendar quarter commencing after the calendar quarter ending on December 31, 2020 (and only during such calendar quarter), if the last reported sale price of the Company’s Class A 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 conversion price on each applicable trading day; (2) during the five ten The Company may not redeem the 2020 Notes prior to October 4, 2022. On or after October 4, 2022, the Company may redeem for cash all or part of the 2020 Notes if the last reported sale price of the Company’s Class A common stock equals or exceeds 130% of the conversion price then in effect for at least 20 trading days (whether or not consecutive), including at least one of the five trading days immediately preceding the date on which the Company provides notice of redemption, during any 30 consecutive trading days ending on, and including the trading day immediately preceding the date on which the Company provides notice of the redemption. The redemption price will be 100% of the principal amount of the 2020 Notes to be redeemed, plus accrued and unpaid interest, if any. Upon the occurrence of a fundamental change (as defined in the 2020 Indenture), holders may require the Company to repurchase all or a portion of their 2020 Notes for cash at a price equal to 100% of the principal amount of the 2020 Notes to be repurchased plus any accrued but unpaid interest to, but excluding, the fundamental change repurchase date. The 2020 Indenture contains customary terms and covenants, including that upon certain events of default occurring and continuing, either the Trustee or the holders of not less than 25% in aggregate principal amount of the 2020 Notes then outstanding may declare the entire principal amount of all the 2020 Notes plus accrued interest, if any, to be immediately due and payable. Proceeds from Non-Accreting Notes Transactions The net proceeds from the sale of the 2017 Notes, 2018 Notes, 2019 Notes, and the 2020 Notes were approximately $420.4 million, $562.0 million, $935.1 million, and $1.5 billion. respectively, after deducting the initial purchasers’ discounts and the offering expenses payable by the Company. The Company used approximately $44.2 million, $93.4 million, $145.7 million, and $255.0 million, respectively, of the net proceeds from the 2017 Notes, 2018 Notes, 2019 Notes, and 2020 Notes to pay the cost of the 2017 Capped Call Transactions, the 2018 Capped Call Transactions, the 2019 Capped Call Transactions, and the 2020 Capped Call Transactions, respectively. Accounting for Non-Accreting Notes In accounting for the issuance of the Non-Accreting Notes, the Company separated the Non-Accreting Notes into liability and equity components. The carrying amount of the liability components were calculated by measuring the fair value of a similar liability that does not have an associated convertible feature. The carrying amount of the equity components, representing the conversion option, which does not meet the criteria for separate accounting as a derivative as it is indexed to the Company's own stock, were determined by deducting the fair value of the liability components from the par value of the Non-Accreting Notes. The differences between the carrying amounts of the Non-Accreting Notes and the liability components represent the debt discounts for the corresponding Non-Accreting Notes, which is recorded as a direct deduction from the related debt liabilities in the Consolidated and Condensed Balance Sheet and amortized to interest expense using the effective interest method over the terms of the corresponding Non-Accreting Notes. The effective interest rate of the 2017 Notes, the 2018 Notes, the 2019 Notes and the 2020 Notes is 6.0%, 8.1%, 6.4%, and 5.2%, respectively. The equity components of the 2017 Notes, the 2018 Notes, the 2019 Notes and the 2020 Notes of approximately $95.8 million, $181.5 million, $280.3 million, and $297.4 million, respectively, are included in additional paid-in capital in the Consolidated and Condensed Balance Sheet and are not remeasured as long as they continue to meet the conditions for equity classification. The Company allocated transaction costs related to the components of the Non-Accreting Notes using the same proportions as the proceeds from the corresponding Non-Accreting Notes. Transaction costs attributable to the liability components were recorded as direct deductions from the related debt liabilities in the Consolidated and Condensed Balance Sheet and amortized to interest expense over the terms of the corresponding Non-Accreting Notes, and transaction costs attributable to the equity components were netted with the corresponding equity components in shareholders’ deficit. 2020 Accreting Notes On April 8, 2020, the Company issued $535.0 million in aggregate original principal amount of 2.50% Accreting Convertible Senior Notes due 2025 (the "2020 Accreting Notes", and collectively with the Non-Accreting Notes, the “Notes”) to GHEP VII Aggregator, L.P. ("Great Hill"), CBEP Investments, LLC ("Charlesbank") and The Spruce House Partnership LLC. The 2020 Accreting Notes are fully and unconditionally guaranteed on a senior unsecured basis by Wayfair LLC, a wholly-owned subsidiary of the Company, as guarantor. The 2020 Accreting Notes were issued pursuant to an indenture, dated April 8, 2020 (the "2020 Accreting Indenture"), among the Company, Wayfair LLC, as guarantor, and U.S. Bank National Association, as trustee. The 2020 Accreting Notes are fully and unconditionally guaranteed on a senior unsecured basis by Wayfair LLC. No cash interest will be payable on the 2020 Accreting Notes. Instead, the 2020 Accreting Notes will accrue interest at a rate of 2.50% per annum which will accrete to the principal amount on April 1 and October 1 of each year, beginning on October 1, 2020. The 2020 Accreting Notes are convertible based upon an initial conversion price of $72.50 per share of the Company’s Class A common stock. The conversion price is subject to adjustment upon the occurrence of certain specified events, including certain distributions and dividends to all or substantially all of the holders of the Company's Class A common stock, but will not be adjusted for accrued and unpaid interest. The Company will settle any conversion of 2020 Accreting Notes with a number of shares of the Company's Class A common stock per $1,000 original principal amount of 2020 Accreting Notes equal to the accreted principal amount of such original principal amount of 2020 Accreting Notes divided by the conversion price. The 2020 Accreting Notes will mature on April 1, 2025, unless earlier purchased, redeemed or converted. Holders may convert all or a portion of their 2020 Accreting Notes at any time prior to the second business day immediately preceding the maturity date. Holders of the 2020 Accreting Notes who convert in connection with a make-whole fundamental change (as defined in the 2020 Accreting Indenture) may be entitled to a premium in the form of additional shares of the Company's Class A common stock. The Company may not redeem the 2020 Accreting Notes prior to May 9, 2023. On or after May 9, 2023, the Company may redeem for cash all or part of the 2020 Accreting Notes if the last reported sale price of the Company's Class A common stock equals or exceeds 276% of the conversion price then in effect for at least 20 trading days (whether or not consecutive), including at least one of the five trading days immediately preceding the date on which the Company provides notice of redemption, during any 30 consecutive trading days ending on, and including the trading day immediately preceding the date on which the Company provides notice of the redemption. The redemption price will be 100% of the accreted principal amount of the 2020 Accreting Notes to be redeemed, including accrued interest, if any, but excluding, the redemption date. Upon the occurrence of a fundamental change (as defined in the 2020 Accreting Indenture), holders may require the Company to repurchase all or a portion of their 2020 Accreting Notes for cash at a price equal to 100% of the accreted principal amount of the 2020 Accreting Notes to be repurchased (which accreted principal amount upon repurchase will include interest, if any, accrued to, but excluding, the fundamental change repurchase date). The 2020 Accreting Indenture contains customary terms and covenants, including that upon certain events of default occurring and continuing, either the Trustee or the holders of not less than 25% in aggregate principal amount of the 2020 Accreting Notes then outstanding may declare the entire principal amount of all the 2020 Accreting Notes plus accrued interest, if any, to be immediately due and payable. The net proceeds from the sale of the 2020 Accreting Notes was approximately $527.4 million, after deducting the offering expenses payable by the Company. In accounting for the issuance of the 2020 Accreting Notes, the Company determined there was a beneficial conversion feature, which represents the excess of the fair value of the underlying common stock at the commitment date less the effective conversion price of the shares convertible at that time. The beneficial conversion feature of $39.4 million was recorded to additional paid-in capital in the Consolidated and Condensed Balance Sheet and represents a debt discount to the 2020 Accreting Notes, which was recorded as a direct deduction from the related debt liability in the Consolidated and Condensed Balance Sheet. It is amortized to interest expense using the effective interest method over the term of the 2020 Accreting Notes. All transaction costs incurred were recorded as a direct deduction from the related debt liability in the Consolidated and Condensed Balance Sheet and are amortized to interest expense using the effective interest method over the term of the 2020 Accreting Notes. The 2020 Accreting Notes accrue interest at a rate of 2.50% per annum, which will accrete to the principal amount on April 1 and October 1 of each year, beginning on October 1, 2020. The interest is amortized to interest expense using the effective interest method over the term of the 2020 Accreting Notes and recorded to other long-term liabilities in the Consolidated and Condensed Balance Sheet. Upon accretion to the principal amount on April 1 and October 1 of each year, the Company will reclassify the interest accrued as of that date to long-term debt. The beneficial conversion feature for additional shares, which would be issued upon conversion of paid in kind interest, is recorded as additional interest expense and additional paid-in capital over the term of the 2020 Accreting Notes as such interest accrues. The effective interest rate of the 2020 Accreting Notes is 4.4%. Capped Call Transactions The Restated 2017 Capped Call Transactions, 2018 Capped Call Transactions, 2019 Capped Call Transactions, and 2020 Capped Call Transactions (collectively, the "Capped Call Transactions") are expected generally to reduce the potential dilution and/or offset the cash payments the Company is required to make in excess of the principal amount of the Non-Accreting Notes upon conversion of the Non-Accreting Notes in the event that the market price per share of the Company’s Class A common stock is greater than the strike price of the Capped Call Transactions (which initially corresponds to the initial conversion price of the Non-Accreting Notes and is subject to certain adjustments under the terms of the Capped Call Transactions), with such reduction and/or offset subject to a cap based on the cap price of the Capped Call Transactions. The Restated 2017 Capped Call Transactions have an initial cap price of $154.16 per share of the Company’s Class A common stock, which represents a premium of 100% over the last reported sale price of the Company’s Class A common stock on September 11, 2017, which is the date the 2017 Notes priced, and is subject to certain adjustments under the terms of the Restated 2017 Capped Call Transactions. The 2018 Capped Call Transactions have an initial cap price of $219.63 per share of the Company’s Class A common stock, which represents a premium of 150% over the last reported sale price of the Company’s Class A common stock on November 14, 2018, which is the day the 2018 Notes priced, and is subject to certain adjustments under the terms of the 2018 Capped Call Transactions. The 2019 Capped Call Transactions have an initial cap price of $280.15 per share of the Company's Class A common stock, which represents a premium of 150% over the last reported sale price of the Company's Class A common stock on August 14, 2019, which is the day the 2019 Notes priced, and is subj

Convertible Debt

Convertible Debt	9 Months Ended
	Sep. 30, 2020
Debt Disclosure [Abstract]
Convertible Debt	14. Credit Agreement The Company has a credit agreement with certain lenders, which currently provides for a $200 million senior secured revolving credit facility maturing on February 21, 2022 (the “Revolver”). The Revolver contains affirmative and negative covenants customarily applicable to senior secured credit facilities, and also requires the Company to maintain certain levels of Free Cash Flow (as defined in the credit agreement). On August 21, 2020, in connection with the 2020 Repurchase Program, the Company amended the credit agreement for the Revolver to increase the Company’s stock repurchase basket in the negative covenant for restricted payments. The Company also increased the revolving loan commitment amount to $200 million on October 30, 2020 through an incremental commitment joinder. In the nine months ended September 30, 2020, the Company borrowed under the Revolver. All borrowings were repaid as of September 30, 2020. As a result, there were no amounts outstanding on the Revolver as of September 30, 2020. 15. Convertible Debt 2017 Notes and Capped Call Transactions On September 15, 2017, the Company issued $431.25 million in aggregate principal amount of 0.375% Convertible Senior Notes due 2022 (the "2017 Notes"), which includes the exercise in full of a $56.25 million over-allotment option, to certain financial institutions as the initial purchasers of the 2017 Notes (the "2017 Initial Purchasers"). On September 11, 2017, in connection with the pricing of the 2017 Notes, the Company entered into privately negotiated capped call transactions (the "2017 Base Capped Call Transactions") with two of the 2017 Initial Purchasers and certain other financial institutions (the "2017 Option Counterparties") and, in connection with the exercise in full of the over-allotment option by the 2017 Initial Purchasers, on September 14, 2017, entered into additional capped call transactions (such additional capped call transactions, the "2017 Additional Capped Call Transactions” and, together with the 2017 Base Capped Call Transactions, the "2017 Capped Call Transactions") with the 2017 Option Counterparties. Collectively, the 2017 Capped Call Transactions covered, initially, the number of shares of the Company’s Class A common stock underlying the 2017 Notes, subject to anti-dilution adjustments substantially similar to those applicable to the 2017 Notes. The 2017 Notes were issued pursuant to an indenture, dated September 15, 2017 (the "2017 Indenture"), between the Company and U.S. Bank National Association, as trustee. The Company pays interest on the 2017 Notes semiannually in arrears at a rate of 0.375% per annum on March 1 and September 1 of each year. The 2017 Notes are convertible based upon an initial conversion rate of 9.6100 shares of the Company’s Class A common stock per $1,000 principal amount of 2017 Notes (equivalent to a conversion price of approximately $104.06 per share of the Company’s Class A common stock). The conversion rate will be subject to adjustment upon the occurrence of certain specified events, including certain distributions and dividends to all or substantially all of the holders of the Company’s Class A common stock, but will not be adjusted for accrued and unpaid interest. The Company will settle any conversions of the 2017 Notes in cash, shares of the Company’s Class A common stock or a combination thereof, with the form of consideration determined at the Company’s election. The 2017 Notes will mature on September 1, 2022, unless earlier purchased, redeemed or converted. Prior to June 1, 2022, holders may convert all or a portion of their 2017 Notes only under the following circumstances: (1) during any calendar quarter (and only during such calendar quarter), if the last reported sale price of the Company’s Class A 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 conversion price on each applicable trading day; (2) during the 5 business day period after any 10 consecutive trading day period (the "2017 Notes measurement period") in which the trading price per $1,000 principal amount of 2017 Notes for each trading day of the 2017 Notes measurement period was less than 98% of the product of the last reported sale price of the Company’s Class A common stock and the conversion rate on each such trading day; (3) with respect to any 2017 Notes called for redemption by the Company, at any time prior to the close of business on the second scheduled trading day immediately preceding the redemption date; or (4) upon the occurrence of specified corporate events. On and after June 1, 2022 until the close of business on the second scheduled trading day immediately preceding the maturity date, holders may convert their 2017 Notes at any time, regardless of the foregoing circumstances. Holders of 2017 Notes who convert their 2017 Notes in connection with a notice of a redemption or a make-whole fundamental change (each as defined in the 2017 Indenture) may be entitled to a premium in the form of an increase in the conversion rate of the 2017 Notes. On November 15, 2018, the Company amended and restated the 2017 Capped Call Transactions (the "Restated 2017 Capped Call Transactions") with each of the 2017 Option Counterparties in order to, among other things, provide that the options underlying the Restated 2017 Capped Call Transactions can, at the Company’s option, remain outstanding until September 1, 2022, which is the maturity date for the 2017 Notes, even if all or a portion of the 2017 Notes are converted, repurchased or redeemed prior to such date. The Company could not redeem the 2017 Notes prior to September 8, 2020. On or after September 8, 2020, the Company may redeem for cash all or part of the 2017 Notes if the last reported sale price of the Company’s Class A common stock equals or exceeds 130% of the conversion price then in effect for at least 20 trading days (whether or not consecutive), including at least one of the five trading days immediately preceding the date on which the Company provides notice of redemption, during any 30 consecutive trading days ending on, and including the trading day immediately preceding the date on which the Company provides notice of the redemption. The redemption price will be 100% of the principal amount of the 2017 Notes to be redeemed, plus accrued and unpaid interest, if any. Upon the occurrence of a fundamental change (as defined in the 2017 Indenture), holders may require the Company to repurchase all or a portion of their 2017 Notes for cash at a price equal to 100% of the principal amount of the 2017 Notes to be repurchased plus any accrued but unpaid interest to, but excluding, the fundamental change repurchase date. The 2017 Indenture contains customary terms and covenants, including that upon certain events of default occurring and continuing, either the Trustee or the holders of not less than 25% in aggregate principal amount of the 2017 Notes then outstanding may declare the entire principal amount of all the 2017 Notes plus accrued interest, if any, to be immediately due and payable. 2018 Notes and Capped Call Transactions In November 2018, the Company issued $575.0 million in aggregate principal amount of 1.125% Convertible Senior Notes due 2024 (the "2018 Notes"), which includes the exercise in full of a $75.0 million option granted to the initial purchasers, to certain financial institutions as the initial purchasers of the 2018 Notes (the "2018 Initial Purchasers"). The issuance of $500.0 million of 2018 Notes closed on November 19, 2018 and the additional $75.0 million of additional 2018 Notes, which were issued pursuant to the exercise of the 2018 Initial Purchasers' option to purchase such additional 2018 Notes, closed on November 29, 2018. On November 14, 2018, in connection with the pricing of the 2018 Notes, the Company entered into privately negotiated capped call transactions (the "2018 Base Capped Call Transactions") with one of the 2018 Initial Purchasers and certain other financial institutions (the "2018 Option Counterparties") and, in connection with the exercise in full of the 2018 Initial Purchasers' option to purchase such additional 2018 Notes, on November 27, 2018, entered into additional capped call transactions (such additional capped call transactions, the "2018 Additional Capped Call Transactions" and, together with the 2018 Base Capped Call Transactions, the "2018 Capped Call Transactions") with the 2018 Option Counterparties. Collectively, the 2018 Capped Call Transactions cover, initially, the number of shares of the Company’s Class A common stock underlying the 2018 Notes, subject to anti-dilution adjustments substantially similar to those applicable to the 2018 Notes. The 2018 Notes were issued pursuant to an indenture, dated November 19, 2018 (the "2018 Indenture"), between the Company and U.S. Bank National Association, as trustee. The Company will pay interest on the 2018 Notes semiannually in arrears at a rate of 1.125% per annum on May 1 and November 1 of each year commencing on May 1, 2019. The 2018 Notes are convertible based upon an initial conversion rate of 8.5910 shares of the Company’s Class A common stock per $1,000 principal amount of 2018 Notes (equivalent to a conversion price of approximately $116.40 per share of the Company’s Class A common stock). The conversion rate will be subject to adjustment upon the occurrence of certain specified events, including certain distributions and dividends to all or substantially all of the holders of the Company’s Class A common stock, but will not be adjusted for accrued and unpaid interest. The Company will settle any conversions of the 2018 Notes in cash, shares of the Company’s Class A common stock or a combination thereof, with the form of consideration determined at the Company’s election. The 2018 Notes will mature on November 1, 2024, unless earlier purchased, redeemed or converted. Prior to August 1, 2024, holders may convert all or a portion of their 2018 Notes only under the following circumstances: (1) during any calendar quarter (and only during such calendar quarter), if the last reported sale price of the Company’s Class A 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 conversion price on each applicable trading day; (2) during the five ten The Company may not redeem the 2018 Notes prior to May 8, 2022. On or after May 8, 2022, the Company may redeem for cash all or part of the 2018 Notes if the last reported sale price of the Company’s Class A common stock equals or exceeds 130% of the conversion price then in effect for at least 20 trading days (whether or not consecutive), including at least one of the five trading days immediately preceding the date on which the Company provides notice of redemption, during any 30 consecutive trading days ending on, and including the trading day immediately preceding the date on which the Company provides notice of the redemption. The redemption price will be 100% of the principal amount of the 2018 Notes to be redeemed, plus accrued and unpaid interest, if any. Upon the occurrence of a fundamental change (as defined in the 2018 Indenture), holders may require the Company to repurchase all or a portion of their 2018 Notes for cash at a price equal to 100% of the principal amount of the 2018 Notes to be repurchased plus any accrued but unpaid interest to, but excluding, the fundamental change repurchase date. The 2018 Indenture contains customary terms and covenants, including that upon certain events of default occurring and continuing, either the Trustee or the holders of not less than 25% in aggregate principal amount of the 2018 Notes then outstanding may declare the entire principal amount of all the 2018 Notes plus accrued interest, if any, to be immediately due and payable. 2019 Notes and Capped Call Transactions On August 19, 2019, the Company issued $948.75 million in aggregate principal amount of 1.00% Convertible Senior Notes due 2026 (the "2019 Notes"), which includes the exercise in full of a $123.75 million option granted to the initial purchasers, to certain financial institutions as the initial purchasers of the 2019 Notes (the "2019 Initial Purchasers"). On August 14, 2019, in connection with the pricing of the 2019 Notes, the Company entered into privately negotiated capped call transactions (the "2019 Base Capped Call Transactions") with certain of the 2019 Initial Purchasers or their affiliates and another financial institution (the "2019 Option Counterparties") and, in connection with the exercise in full of the 2019 Initial Purchasers' option to purchase such additional 2019 Notes, on August 16, 2019, entered into additional capped call transactions (such additional capped call transactions, the "2019 Additional Capped Call Transactions" and, together with the 2019 Base Capped Call Transactions, the "2019 Capped Call Transactions") with the 2019 Option Counterparties. Collectively, the 2019 Capped Call Transactions cover, initially, the number of shares of the Company’s Class A common stock underlying the 2019 Notes, subject to anti-dilution adjustments substantially similar to those applicable to the 2019 Notes. The 2019 Notes were issued pursuant to an indenture, dated August 19, 2019 (the "2019 Indenture"), between the Company and U.S. Bank National Association, as trustee. The Company will pay interest on the 2019 Notes semiannually in arrears at a rate of 1.00% per annum on February 15 and August 15 of each year commencing on February 15, 2020. The 2019 Notes are convertible based upon an initial conversion rate of 6.7349 shares of the Company’s Class A common stock per $1,000 principal amount of 2019 Notes (equivalent to a conversion price of approximately $148.48 per share of the Company’s Class A common stock). The conversion rate will be subject to adjustment upon the occurrence of certain specified events, including certain distributions and dividends to all or substantially all of the holders of the Company’s Class A common stock, but will not be adjusted for accrued and unpaid interest. The Company will settle any conversions of the 2019 Notes in cash, shares of the Company’s Class A common stock or a combination thereof, with the form of consideration determined at the Company’s election. The 2019 Notes will mature on August 15, 2026, unless earlier purchased, redeemed or converted. Prior to May 15, 2026, holders may convert all or a portion of their 2019 Notes only under the following circumstances: (1) during any calendar quarter commencing after the calendar quarter ending on December 31, 2019 (and only during such calendar quarter), if the last reported sale price of the Company’s Class A 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 conversion price on each applicable trading day; (2) during the five ten The Company may not redeem the 2019 Notes prior to August 20, 2023. On or after August 20, 2023, the Company may redeem for cash all or part of the 2019 Notes if the last reported sale price of the Company’s Class A common stock equals or exceeds 130% of the conversion price then in effect for at least 20 trading days (whether or not consecutive), including at least one of the five trading days immediately preceding the date on which the Company provides notice of redemption, during any 30 consecutive trading days ending on, and including the trading day immediately preceding the date on which the Company provides notice of the redemption. The redemption price will be 100% of the principal amount of the 2019 Notes to be redeemed, plus accrued and unpaid interest, if any. Upon the occurrence of a fundamental change (as defined in the 2019 Indenture), holders may require the Company to repurchase all or a portion of their 2019 Notes for cash at a price equal to 100% of the principal amount of the 2019 Notes to be repurchased plus any accrued but unpaid interest to, but excluding, the fundamental change repurchase date. The 2019 Indenture contains customary terms and covenants, including that upon certain events of default occurring and continuing, either the Trustee or the holders of not less than 25% in aggregate principal amount of the 2019 Notes then outstanding may declare the entire principal amount of all the 2019 Notes plus accrued interest, if any, to be immediately due and payable. 2020 Notes and Capped Call Transactions On August 14, 2020, the Company issued $1.518 billion in aggregate principal amount of 0.625% Convertible Senior Notes due 2025 (the “2020 Notes”, and together with the 2017 Notes, the 2018 Notes and the 2019 Notes, the “Non-Accreting Notes”), which includes the exercise in full of a $198.0 million option granted to the initial purchasers, to certain financial institutions as the initial purchasers of the 2020 Notes (the “2020 Initial Purchasers”). On August 11, 2020, in connection with the pricing of the 2020 Notes, the Company entered into privately negotiated capped call transactions (the “2020 Base Capped Call Transactions”) with certain of the 2020 Initial Purchasers or their respective affiliates and certain other financial institutions (the “2020 Option Counterparties”) and, in connection with the exercise in full of the 2020 Initial Purchasers’ option to purchase such additional 2020 Notes, on August 12, 2020, entered into additional capped call transactions (such additional capped call transactions, the “2020 Additional Capped Call Transactions” and together with the 2020 Base Capped Call Transactions, the “2020 Capped Call Transactions”) with the 2020 Option Counterparties. Collectively, the 2020 Capped Call Transactions cover, initially, the number of shares of the Company’s Class A common stock underlying the 2020 Notes, subject to anti-dilution adjustments substantially similar to those applicable to the 2020 Notes. The 2020 Notes were issued pursuant to an indenture, dated August 14, 2020 (the "2020 Indenture"), between the Company and U.S. Bank National Association, as trustee. The Company will pay interest on the 2020 Notes semiannually in arrears at a rate of 0.625% per annum on April 1 and October 1 of each year commencing on April 1, 2021. The 2020 Notes are convertible based upon an initial conversion rate of 2.3972 shares of the Company’s Class A common stock per $1,000 principal amount of 2020 Notes (equivalent to a conversion price of approximately $417.15 per share of the Company’s Class A common stock). The conversion rate will be subject to adjustment upon the occurrence of certain specified events, including certain distributions and dividends to all or substantially all of the holders of the Company’s Class A common stock, but will not be adjusted for accrued and unpaid interest. The Company will settle any conversions of the 2020 Notes in cash, shares of the Company’s Class A common stock or a combination thereof, with the form of consideration determined at the Company’s election. The 2020 Notes will mature on October 1, 2025, unless earlier purchased, redeemed or converted. Prior to July 1, 2025, holders may convert all or a portion of their 2020 Notes only under the following circumstances: (1) during any calendar quarter commencing after the calendar quarter ending on December 31, 2020 (and only during such calendar quarter), if the last reported sale price of the Company’s Class A 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 conversion price on each applicable trading day; (2) during the five ten The Company may not redeem the 2020 Notes prior to October 4, 2022. On or after October 4, 2022, the Company may redeem for cash all or part of the 2020 Notes if the last reported sale price of the Company’s Class A common stock equals or exceeds 130% of the conversion price then in effect for at least 20 trading days (whether or not consecutive), including at least one of the five trading days immediately preceding the date on which the Company provides notice of redemption, during any 30 consecutive trading days ending on, and including the trading day immediately preceding the date on which the Company provides notice of the redemption. The redemption price will be 100% of the principal amount of the 2020 Notes to be redeemed, plus accrued and unpaid interest, if any. Upon the occurrence of a fundamental change (as defined in the 2020 Indenture), holders may require the Company to repurchase all or a portion of their 2020 Notes for cash at a price equal to 100% of the principal amount of the 2020 Notes to be repurchased plus any accrued but unpaid interest to, but excluding, the fundamental change repurchase date. The 2020 Indenture contains customary terms and covenants, including that upon certain events of default occurring and continuing, either the Trustee or the holders of not less than 25% in aggregate principal amount of the 2020 Notes then outstanding may declare the entire principal amount of all the 2020 Notes plus accrued interest, if any, to be immediately due and payable. Proceeds from Non-Accreting Notes Transactions The net proceeds from the sale of the 2017 Notes, 2018 Notes, 2019 Notes, and the 2020 Notes were approximately $420.4 million, $562.0 million, $935.1 million, and $1.5 billion. respectively, after deducting the initial purchasers’ discounts and the offering expenses payable by the Company. The Company used approximately $44.2 million, $93.4 million, $145.7 million, and $255.0 million, respectively, of the net proceeds from the 2017 Notes, 2018 Notes, 2019 Notes, and 2020 Notes to pay the cost of the 2017 Capped Call Transactions, the 2018 Capped Call Transactions, the 2019 Capped Call Transactions, and the 2020 Capped Call Transactions, respectively. Accounting for Non-Accreting Notes In accounting for the issuance of the Non-Accreting Notes, the Company separated the Non-Accreting Notes into liability and equity components. The carrying amount of the liability components were calculated by measuring the fair value of a similar liability that does not have an associated convertible feature. The carrying amount of the equity components, representing the conversion option, which does not meet the criteria for separate accounting as a derivative as it is indexed to the Company's own stock, were determined by deducting the fair value of the liability components from the par value of the Non-Accreting Notes. The differences between the carrying amounts of the Non-Accreting Notes and the liability components represent the debt discounts for the corresponding Non-Accreting Notes, which is recorded as a direct deduction from the related debt liabilities in the Consolidated and Condensed Balance Sheet and amortized to interest expense using the effective interest method over the terms of the corresponding Non-Accreting Notes. The effective interest rate of the 2017 Notes, the 2018 Notes, the 2019 Notes and the 2020 Notes is 6.0%, 8.1%, 6.4%, and 5.2%, respectively. The equity components of the 2017 Notes, the 2018 Notes, the 2019 Notes and the 2020 Notes of approximately $95.8 million, $181.5 million, $280.3 million, and $297.4 million, respectively, are included in additional paid-in capital in the Consolidated and Condensed Balance Sheet and are not remeasured as long as they continue to meet the conditions for equity classification. The Company allocated transaction costs related to the components of the Non-Accreting Notes using the same proportions as the proceeds from the corresponding Non-Accreting Notes. Transaction costs attributable to the liability components were recorded as direct deductions from the related debt liabilities in the Consolidated and Condensed Balance Sheet and amortized to interest expense over the terms of the corresponding Non-Accreting Notes, and transaction costs attributable to the equity components were netted with the corresponding equity components in shareholders’ deficit. 2020 Accreting Notes On April 8, 2020, the Company issued $535.0 million in aggregate original principal amount of 2.50% Accreting Convertible Senior Notes due 2025 (the "2020 Accreting Notes", and collectively with the Non-Accreting Notes, the “Notes”) to GHEP VII Aggregator, L.P. ("Great Hill"), CBEP Investments, LLC ("Charlesbank") and The Spruce House Partnership LLC. The 2020 Accreting Notes are fully and unconditionally guaranteed on a senior unsecured basis by Wayfair LLC, a wholly-owned subsidiary of the Company, as guarantor. The 2020 Accreting Notes were issued pursuant to an indenture, dated April 8, 2020 (the "2020 Accreting Indenture"), among the Company, Wayfair LLC, as guarantor, and U.S. Bank National Association, as trustee. The 2020 Accreting Notes are fully and unconditionally guaranteed on a senior unsecured basis by Wayfair LLC. No cash interest will be payable on the 2020 Accreting Notes. Instead, the 2020 Accreting Notes will accrue interest at a rate of 2.50% per annum which will accrete to the principal amount on April 1 and October 1 of each year, beginning on October 1, 2020. The 2020 Accreting Notes are convertible based upon an initial conversion price of $72.50 per share of the Company’s Class A common stock. The conversion price is subject to adjustment upon the occurrence of certain specified events, including certain distributions and dividends to all or substantially all of the holders of the Company's Class A common stock, but will not be adjusted for accrued and unpaid interest. The Company will settle any conversion of 2020 Accreting Notes with a number of shares of the Company's Class A common stock per $1,000 original principal amount of 2020 Accreting Notes equal to the accreted principal amount of such original principal amount of 2020 Accreting Notes divided by the conversion price. The 2020 Accreting Notes will mature on April 1, 2025, unless earlier purchased, redeemed or converted. Holders may convert all or a portion of their 2020 Accreting Notes at any time prior to the second business day immediately preceding the maturity date. Holders of the 2020 Accreting Notes who convert in connection with a make-whole fundamental change (as defined in the 2020 Accreting Indenture) may be entitled to a premium in the form of additional shares of the Company's Class A common stock. The Company may not redeem the 2020 Accreting Notes prior to May 9, 2023. On or after May 9, 2023, the Company may redeem for cash all or part of the 2020 Accreting Notes if the last reported sale price of the Company's Class A common stock equals or exceeds 276% of the conversion price then in effect for at least 20 trading days (whether or not consecutive), including at least one of the five trading days immediately preceding the date on which the Company provides notice of redemption, during any 30 consecutive trading days ending on, and including the trading day immediately preceding the date on which the Company provides notice of the redemption. The redemption price will be 100% of the accreted principal amount of the 2020 Accreting Notes to be redeemed, including accrued interest, if any, but excluding, the redemption date. Upon the occurrence of a fundamental change (as defined in the 2020 Accreting Indenture), holders may require the Company to repurchase all or a portion of their 2020 Accreting Notes for cash at a price equal to 100% of the accreted principal amount of the 2020 Accreting Notes to be repurchased (which accreted principal amount upon repurchase will include interest, if any, accrued to, but excluding, the fundamental change repurchase date). The 2020 Accreting Indenture contains customary terms and covenants, including that upon certain events of default occurring and continuing, either the Trustee or the holders of not less than 25% in aggregate principal amount of the 2020 Accreting Notes then outstanding may declare the entire principal amount of all the 2020 Accreting Notes plus accrued interest, if any, to be immediately due and payable. The net proceeds from the sale of the 2020 Accreting Notes was approximately $527.4 million, after deducting the offering expenses payable by the Company. In accounting for the issuance of the 2020 Accreting Notes, the Company determined there was a beneficial conversion feature, which represents the excess of the fair value of the underlying common stock at the commitment date less the effective conversion price of the shares convertible at that time. The beneficial conversion feature of $39.4 million was recorded to additional paid-in capital in the Consolidated and Condensed Balance Sheet and represents a debt discount to the 2020 Accreting Notes, which was recorded as a direct deduction from the related debt liability in the Consolidated and Condensed Balance Sheet. It is amortized to interest expense using the effective interest method over the term of the 2020 Accreting Notes. All transaction costs incurred were recorded as a direct deduction from the related debt liability in the Consolidated and Condensed Balance Sheet and are amortized to interest expense using the effective interest method over the term of the 2020 Accreting Notes. The 2020 Accreting Notes accrue interest at a rate of 2.50% per annum, which will accrete to the principal amount on April 1 and October 1 of each year, beginning on October 1, 2020. The interest is amortized to interest expense using the effective interest method over the term of the 2020 Accreting Notes and recorded to other long-term liabilities in the Consolidated and Condensed Balance Sheet. Upon accretion to the principal amount on April 1 and October 1 of each year, the Company will reclassify the interest accrued as of that date to long-term debt. The beneficial conversion feature for additional shares, which would be issued upon conversion of paid in kind interest, is recorded as additional interest expense and additional paid-in capital over the term of the 2020 Accreting Notes as such interest accrues. The effective interest rate of the 2020 Accreting Notes is 4.4%. Capped Call Transactions The Restated 2017 Capped Call Transactions, 2018 Capped Call Transactions, 2019 Capped Call Transactions, and 2020 Capped Call Transactions (collectively, the "Capped Call Transactions") are expected generally to reduce the potential dilution and/or offset the cash payments the Company is required to make in excess of the principal amount of the Non-Accreting Notes upon conversion of the Non-Accreting Notes in the event that the market price per share of the Company’s Class A common stock is greater than the strike price of the Capped Call Transactions (which initially corresponds to the initial conversion price of the Non-Accreting Notes and is subject to certain adjustments under the terms of the Capped Call Transactions), with such reduction and/or offset subject to a cap based on the cap price of the Capped Call Transactions. The Restated 2017 Capped Call Transactions have an initial cap price of $154.16 per share of the Company’s Class A common stock, which represents a premium of 100% over the last reported sale price of the Company’s Class A common stock on September 11, 2017, which is the date the 2017 Notes priced, and is subject to certain adjustments under the terms of the Restated 2017 Capped Call Transactions. The 2018 Capped Call Transactions have an initial cap price of $219.63 per share of the Company’s Class A common stock, which represents a premium of 150% over the last reported sale price of the Company’s Class A common stock on November 14, 2018, which is the day the 2018 Notes priced, and is subject to certain adjustments under the terms of the 2018 Capped Call Transactions. The 2019 Capped Call Transactions have an initial cap price of $280.15 per share of the Company's Class A common stock, which represents a premium of 150% over the last reported sale price of the Company's Class A common stock on August 14, 2019, which is the day the 2019 Notes priced, and is subj

Earning (Loss) per Share

Earning (Loss) per Share	9 Months Ended
	Sep. 30, 2020
Earnings Per Share [Abstract]
Earnings (Loss) per Share	16. Earnings (Loss) per Share Basic and diluted earnings (loss) per share is presented using the two-class method required for participating securities: Class A and Class B common stock. The rights of the holders of Class A and Class B common stock are identical, except with respect to voting and conversion. For more information on the rights of Class A and Class B common stockholders, see Note 13, Stockholders’ Deficit . Basic earnings (loss) per share is computed using the weighted-average number of shares of common stock outstanding during the period. Diluted earnings (loss) per share is computed using the weighted-average number of shares of common stock plus, if dilutive, common stock equivalents outstanding during the period and stock issuable upon conversion of our convertible debt instruments. The Company's common stock equivalents consist of shares issuable upon the release of RSUs, and to a lesser extent, the incremental shares of common stock issuable upon the exercise of stock options and unvested restricted stock. The dilutive effect of these common stock equivalents is reflected in diluted earnings (loss) per share by application of the treasury stock method. The dilutive effect of shares issuable upon conversion of the Company's convertible debt instruments are included in the calculation of diluted net earnings (loss) per share under the if-converted method. For periods in which the Company has generated a net loss, the Company's basic and diluted earnings (loss) per share are the same as basic earnings (loss) per share, as the effects of common stock equivalents outstanding and shares issuable upon conversion of convertible debt instruments are antidilutive and therefore excluded from the calculation of diluted earnings (loss) per share. The Company allocates undistributed earnings between the classes on a one-to-one basis when computing earnings (loss) per share. As a result, basic and diluted earnings (loss) per Class A and Class B shares of common stock are equivalent. The following table presents the calculation of basic and diluted earnings (loss) per share: Three months ended September 30, Nine months ended September 30, 2020 2019 2020 2019 (in thousands, except per share data) Numerator: Numerator for basic EPS - Net income (loss) $ 173,166 $ (272,035) $ 161,178 $ (654,362) Effect of dilutive securities: Interest expense associated with convertible debt instruments 9,136 — — — Numerator for diluted EPS - net income (loss) available to common stockholders after the effect of dilutive securities $ 182,302 $ (272,035) $ 161,178 $ (654,362) Denominator: Denominator for basic EPS - weighted-average number of shares of common stock outstanding 95,373 92,540 94,767 91,820 Effect of dilutive securities: Employee stock options 24 — 32 — Restricted stock units 4,123 — 3,222 — Convertible debt instruments 9,680 — — — Dilutive potential common shares 13,827 — 3,254 — Denominator for diluted EPS - adjusted weighted-average number of shares of common stock outstanding after the effect of dilutive securities 109,200 92,540 98,021 91,820 Basic earnings (loss) per share $ 1.82 $ (2.94) $ 1.70 $ (7.13) Diluted earnings (loss) per share $ 1.67 $ (2.94) $ 1.64 $ (7.13) The potential common shares from anti-dilutive securities excluded from the weighted-average shares of common stock used to calculate diluted earnings (loss) per share were as follows: Three months ended September 30, Nine months ended September 30, 2020 2019 2020 2019 (in thousands) Outstanding employee stock options — 51 — 51 Unvested restricted common stock — 20 — 20 Unvested restricted stock units 116 7,823 510 7,823 Shares related to convertible debt instruments 13,228 15,474 20,232 15,474 Total 13,344 23,368 20,742 23,368 The Company may settle conversions of the Non-Accreting Notes in cash, shares of the Company's Class A common stock or any combination thereof at its election. The Company will settle conversions of the 2020 Accreting Notes in shares. T he Capped Call Transactions are generally expected to reduce the potential dilution of the Company's Class A common stock upon any conversion of Notes and/or offset the cash payments the Company is required to make in excess of the principal amount of the Notes. The number of shares of the Company's Class A common stock potentially issuable and obtainable at the respective conversion prices of the Notes and the Capped Call Transactions, respectively, by year, are as follows: 2017 Notes / Restated 2017 Capped Call Transactions 2018 Notes / 2018 Capped Call Transactions 2019 Notes / 2019 Capped Call Transactions 2020 Accreting Notes 2020 Notes / 2020 Capped Call Transactions (in thousands) Shares potentially issuable from convertible debt instruments 261 4,940 6,390 7,379 3,639 Shares obtainable from the exercise of capped call transactions (1,347) (2,322) (3,003) — (1,710) Total (1,086) 2,618 3,387 7,379 1,929 For more information on the structure of the Notes and the Capped Call Transactions, including potential adjustments to the conversion prices used to determine the shares presented in the preceding table, see Note 15, Convertible Debt .

Related Party Transactions

Related Party Transactions	9 Months Ended
	Sep. 30, 2020
Related Party Transactions [Abstract]
Related Party Transactions	17. Related Party Transactions As discussed in Note 15, Convertible Debt , on April 8, 2020, pursuant to the terms of the amended and restated purchase agreement, dated April 7, 2020 (the "Purchase Agreement"), the Company issued $535.0 million in aggregate original principal amount of 2020 Accreting Notes. The issuance of the 2020 Accreting Notes constitutes a related party transaction because of Michael W. Choe's positions as a director of the Company (as of May 12, 2020) and Managing Director and Chief Executive Officer of Charlesbank Capital Partners, LLC, the sole owner of the ultimate general partner of Charlesbank, a party to the Purchase Agreement; Michael Kumin's positions as a director of the Company and a Managing Partner at Great Hill Partners, LP, Manager of the ultimate general partner of Great Hill, a party to the Purchase Agreement; and the limited partnership interests held by Niraj Shah and Steve Conine, the Company's co-founders and co-chairmen, in affiliates of Great Hill and Charlesbank.

Recent Accounting Pronouncement

Recent Accounting Pronouncements	9 Months Ended
	Sep. 30, 2020
Accounting Policies [Abstract]
Recent Accounting Pronouncements	2. Summary of Significant Accounting Policies Basis of Presentation The accompanying unaudited Consolidated and Condensed Financial Statements contained in this Quarterly Report on Form 10-Q are those of the Company and have been prepared in accordance with generally accepted accounting principles in the United States ("GAAP") and applicable rules and regulations of the U.S. Securities and Exchange Commission ("SEC") regarding interim financial reporting. Certain information and note disclosures normally included in the audited financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. As such, the information included in this Quarterly Report on Form 10-Q should be read in conjunction with the audited consolidated financial statements and accompanying notes included in our Annual Report on Form 10-K for the year ended December 31, 2019. The Consolidated and Condensed Balance Sheet as of December 31, 2019 included herein was derived from the audited financial statements as of that date, but does not include all disclosures including notes required by GAAP. The accompanying unaudited Consolidated and Condensed Financial Statements have been prepared on the same basis as the audited consolidated financial statements and, in the opinion of management, reflect all adjustments, consisting of normal recurring adjustments, that are necessary to present fairly the results of the interim periods presented. Interim results are not necessarily indicative of the results for the full year ended December 31, 2020 or future periods. The Company believes that other than the implementation of Accounting Standards Update (“ASU”) No. 2016-13, Financial Instruments – Credit Losses (Topic 326), Measurement of Credit Losses on Financial Instruments ("ASU 2016-13"), there have been no significant changes during the nine months ended September 30, 2020 to the items disclosed in Note 2, Summary of Significant Accounting Policies , included in Part II, Item 8, Financial Statements and Supplementary Data , of the Company’s Annual Report on Form 10-K for the year ended December 31, 2019. Principles of Consolidation The accompanying unaudited Consolidated and Condensed Financial Statements of Wayfair Inc. include its wholly-owned subsidiaries. All intercompany accounts and transactions have been eliminated. Use of Estimates The preparation of the unaudited Consolidated and Condensed Financial Statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, and disclosure of contingent assets and liabilities, at the date of the financial statements and the reported amounts of net revenues and expenses during the reporting period. Actual results could differ from those estimates. Earnings (Loss) per Share The Company follows the two-class method when computing earnings (loss) per share for its two issued classes of common stock - Class A and Class B. Basic earnings (loss) per share is computed using the weighted-average number of shares of common stock outstanding during the period. Diluted earnings (loss) per share is computed using the weighted-average number of shares of common stock outstanding during the period plus, if dilutive, stock awards, including stock options and restricted stock units, as determined under the treasury stock method, and convertible debt instruments, as determined under the if-converted method. In periods when we have a net loss, stock awards and convertible debt instruments are excluded from our calculations of earnings per share as their inclusion would have an antidilutive effect. Credit Impairment The Company adopted ASU No. 2016-13 on January 1, 2020 using the modified retrospective transition method. This ASU revises how entities account for credit losses for most financial assets and certain other instruments that are not measured at fair value through net income. As of January 1, 2020, the adoption of ASU 2016-13 Credit Losses , for additional detail. 18. Recent Accounting Pronouncements In August 2020, the FASB issued ASU No. 2020-06, Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging—Contracts in Entity’s Own Equity (Subtopic 815-40) (“ASU 2020-06”). This ASU simplifies the accounting for convertible instruments by removing the separation models for convertible debt with cash conversion features and convertible instruments with a beneficial conversion feature. Under ASU 2020-06, a convertible debt instrument with those features will generally be reported as a single liability at its amortized cost with no separate accounting for the embedded conversion features. We expect the elimination of these models will reduce reported interest expense and increase reported net income for the Company’s existing convertible instruments falling under the scope of those models before the adoption of ASU 2020-06. ASU 2020-06 requires the application of the if-converted method when calculating diluted earnings per share, eliminating the Company’s ability to use the treasury stock method when certain conditions are met. The ASU is effective for annual reporting periods beginning after December 15, 2021, with early adoption permitted no earlier than fiscal years

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2020
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited Consolidated and Condensed Financial Statements contained in this Quarterly Report on Form 10-Q are those of the Company and have been prepared in accordance with generally accepted accounting principles in the United States ("GAAP") and applicable rules and regulations of the U.S. Securities and Exchange Commission ("SEC") regarding interim financial reporting. Certain information and note disclosures normally included in the audited financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations. As such, the information included in this Quarterly Report on Form 10-Q should be read in conjunction with the audited consolidated financial statements and accompanying notes included in our Annual Report on Form 10-K for the year ended December 31, 2019. The Consolidated and Condensed Balance Sheet as of December 31, 2019 included herein was derived from the audited financial statements as of that date, but does not include all disclosures including notes required by GAAP. The accompanying unaudited Consolidated and Condensed Financial Statements have been prepared on the same basis as the audited consolidated financial statements and, in the opinion of management, reflect all adjustments, consisting of normal recurring adjustments, that are necessary to present fairly the results of the interim periods presented. Interim results are not necessarily indicative of the results for the full year ended December 31, 2020 or future periods.
New Accounting Policies	The Company believes that other than the implementation of Accounting Standards Update (“ASU”) No. 2016-13, Financial Instruments – Credit Losses (Topic 326), Measurement of Credit Losses on Financial Instruments ("ASU 2016-13"), there have been no significant changes during the nine months ended September 30, 2020 to the items disclosed in Note 2, Summary of Significant Accounting Policies , included in Part II, Item 8, Financial Statements and Supplementary Data , of the Company’s Annual Report on Form 10-K for the year ended December 31, 2019. Credit Impairment The Company adopted ASU No. 2016-13 on January 1, 2020 using the modified retrospective transition method. This ASU revises how entities account for credit losses for most financial assets and certain other instruments that are not measured at fair value through net income. As of January 1, 2020, the adoption of ASU 2016-13 Credit Losses
Principles of Consolidation	Principles of Consolidation The accompanying unaudited Consolidated and Condensed Financial Statements of Wayfair Inc. include its wholly-owned subsidiaries. All intercompany accounts and transactions have been eliminated.
Use of Estimates	Use of Estimates
Earnings (Loss) per Share	Earnings (Loss) per Share The Company follows the two-class method when computing earnings (loss) per share for its two issued classes of common stock - Class A and Class B. Basic earnings (loss) per share is computed using the weighted-average number of shares of common stock outstanding during the period. Diluted earnings (loss) per share is computed using the weighted-average number of shares of common stock outstanding during the period plus, if dilutive, stock awards, including stock options and restricted stock units, as determined under the treasury stock method, and convertible debt instruments, as determined under the if-converted method. In periods when we have a net loss, stock awards and convertible debt instruments are excluded from our calculations of earnings per share as their inclusion would have an antidilutive effect.
Credit Impairment	Accounts receivable are stated net of the allowance for credit losses, which are recorded based on historical losses as well as management's expectation of future collections. Uncollectible amounts are written off against the allowance after all collection efforts have been exhausted. The Company's exposure to credit loss is minimized through fraud assessments performed prior to customer checkout and the Company's policy of monitoring the creditworthiness of its customers to which it grants credit terms in the normal course of business.

Investments and Fair Value Me_2

Investments and Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2020
Fair Value Disclosures [Abstract]
Schedule of Marketable Securities	The following tables present details of the Company’s investments as of September 30, 2020 and December 31, 2019: September 30, 2020 Amortized Gross Gross Estimated (in thousands) Short-term: Investment securities $ 113,886 $ 99 $ — $ 113,985 Total $ 113,886 $ 99 $ — $ 113,985 December 31, 2019 Amortized Gross Unrealized Gains Gross Estimated (in thousands) Short-term: Investment securities $ 404,294 $ 20 $ (62) $ 404,252 Long-term: Investment securities 155,616 92 (18) 155,690 Total $ 559,910 $ 112 $ (80) $ 559,942
Schedule of the Fair Value of the Company's Financial Assets Measured at Fair Value on a Recurring Basis Based on the Three-Tier Value Hierarchy	The following tables set forth the fair value of the Company’s financial assets measured at fair value on a recurring basis as of September 30, 2020 and December 31, 2019 based on the three-tier value hierarchy: September 30, 2020 Level 1 Level 2 Level 3 Total (in thousands) Cash and cash equivalents: Cash $ 538,767 $ — $ — $ 538,767 Cash equivalents 1,904,172 — — 1,904,172 Total cash and cash equivalents 2,442,939 — — 2,442,939 Short-term investments: Investment securities — 113,985 — 113,985 Other non-current assets: Certificate of deposit 5,200 — — 5,200 Total $ 2,448,139 $ 113,985 $ — $ 2,562,124 December 31, 2019 Level 1 Level 2 Level 3 Total (in thousands) Cash and cash equivalents: Cash $ 308,521 $ — $ — $ 308,521 Cash equivalents 274,232 — — 274,232 Total cash and cash equivalents 582,753 — — 582,753 Short-term investments: Investment securities — 404,252 — 404,252 Other non-current assets: Certificate of deposit 5,076 — — 5,076 Long-term investments: Investment securities — 155,690 — 155,690 Total $ 587,829 $ 559,942 $ — $ 1,147,771

Property and Equipment, net (Ta

Property and Equipment, net (Tables)	9 Months Ended
	Sep. 30, 2020
Property, Plant and Equipment [Abstract]
Schedule of Property and Equipment, net	The following table summarizes property and equipment, net as of September 30, 2020 and December 31, 2019: September 30, December 31, (in thousands) Furniture and computer equipment $ 554,489 $ 509,120 Site and software development costs 397,027 297,252 Leasehold improvements 341,345 228,514 Construction in progress 23,667 45,503 1,316,528 1,080,389 Less accumulated depreciation and amortization (634,471) (455,845) Property and equipment, net $ 682,057 $ 624,544

Leases (Tables)

Leases (Tables)	9 Months Ended
	Sep. 30, 2020
Leases [Abstract]
Other Information Related to Leases	The following table presents supplemental cash flow information related to leases: Nine months ended September 30, 2020 Nine months ended September 30, 2019 (in thousands) Cash payments included in operating cash flows from lease arrangements $ 105,416 $ 77,687 Right-of-use assets obtained in exchange for lease obligations $ 110,210 $ 281,006
Supplemental Balance Sheet Information	The following table presents supplemental balance sheet information related to leases: September 30, 2020 December 31, 2019 Additional lease information Weighted average remaining lease term 8 years 10 years Weighted average discount rate 6.5 % 6.7 %
Future Minimum Lease Payments	The following table presents future minimum lease payments under non-cancellable leases as of September 30, 2020: Amount (in thousands) 2020 (excluding the nine months ended September 30, 2020) $ 33,793 2021 161,998 2022 162,800 2023 157,581 2024 155,062 Thereafter 602,837 Total future minimum lease payments 1,274,071 Less: Imputed interest (303,994) Total $ 970,077
Operating Lease Balance Sheet Items	The following table presents total operating leases as of September 30, 2020 and December 31, 2019: September 30, December 31, (in thousands) Balance sheet line item Other current liabilities $ 102,366 $ 91,104 Operating lease liabilities 867,711 822,602 Total operating leases $ 970,077 $ 913,706

Equity-Based Compensation (Tabl

Equity-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2020
Share-based Payment Arrangement [Abstract]
Summary of Activity Relating to Stock Options	The following table presents activity relating to stock options for the nine months ended September 30, 2020: Shares Weighted-Average Exercise Price Weighted-Average Remaining Contractual Term (Years) Outstanding at December 31, 2019 43,606 $ 3.00 1.5 Options exercised (23,660) $ 3.02 Outstanding and exercisable at September 30, 2020 19,946 $ 2.98 0.7
Summary of Activity Relating to RSUs	The following table presents activity relating to RSUs for the nine months ended September 30, 2020: Shares Weighted- Outstanding at December 31, 2019 8,112,736 $ 95.69 RSUs granted 1,688,442 $ 171.72 RSUs vested (2,233,708) $ 95.30 RSUs forfeited/canceled (1,343,119) $ 103.73 Outstanding as of September 30, 2020 6,224,351 $ 115.27

Segment and Geographic Inform_2

Segment and Geographic Information (Tables)	9 Months Ended
	Sep. 30, 2020
Segment Reporting [Abstract]
Activity Related to Net Revenue, Adjusted EBITDA by Segment	The following tables present net revenues and Adjusted EBITDA attributable to the Company's reportable segments for the periods presented: Three months ended September 30, Nine months ended September 30, 2020 2019 2020 2019 (in thousands) U.S. net revenue $ 3,274,872 $ 1,966,654 $ 8,901,559 $ 5,624,870 International net revenue 564,698 338,833 1,572,746 968,697 Total net revenue $ 3,839,570 $ 2,305,487 $ 10,474,305 $ 6,593,567 Three months ended September 30, Nine months ended September 30, 2020 2019 2020 2019 (in thousands) Adjusted EBITDA: U.S. $ 377,007 $ (62,878) $ 766,486 $ (91,002) International (5,895) (81,306) (82,838) (225,383) Total reportable segments Adjusted EBITDA 371,112 (144,184) 683,648 (316,385) Less: reconciling items (1) (197,946) (127,851) (522,470) (337,977) Net income (loss) $ 173,166 $ (272,035) $ 161,178 $ (654,362) (1) The following adjustments are made to reconcile total reportable segments Adjusted EBITDA to consolidated net income (loss): Three months ended September 30, Nine months ended September 30, 2020 2019 2020 2019 (in thousands) Depreciation and amortization $ 72,575 $ 50,250 $ 208,532 $ 134,172 Equity-based compensation and related taxes 76,683 65,275 211,376 173,963 Interest expense, net 36,315 14,432 87,472 33,922 Other expense (income), net 13,584 (2,182) 10,720 (5,582) (Benefit) provision for income taxes, net (1,211) 76 414 1,502 Other (1) — — 3,956 — Total reconciling items $ 197,946 $ 127,851 $ 522,470 $ 337,977

Convertible Debt (Tables)

Convertible Debt (Tables)	9 Months Ended
	Sep. 30, 2020
Debt Disclosure [Abstract]
Schedule of Outstanding Principal Amount and Carrying Value of Notes	The following table presents the outstanding principal amount and carrying value of the Notes as of the date presented: September 30, 2020 December 31, 2019 2017 Notes 2018 Notes 2019 Notes 2020 Accreting Notes 2020 Notes 2017 Notes 2018 Notes 2019 Notes (in thousands) Principal amounts: Principal $ 27,171 $ 575,000 $ 948,750 $ 535,000 $ 1,518,000 $ 431,250 $ 575,000 $ 948,750 Unamortized debt discount (2,764) (140,200) (251,548) (42,650) (304,624) (59,830) (161,275) (277,700) Net carrying amount $ 24,407 $ 434,800 $ 697,202 $ 492,350 $ 1,213,376 $ 371,420 $ 413,725 $ 671,050
Schedule of Interest Expense Related to Notes	The following tables present total interest expense recognized related to the Notes: Three Months Ended September 30, 2020 2019 2017 Notes 2018 Notes 2019 Notes 2020 Accreting Notes 2020 Notes 2017 Notes 2018 Notes 2019 Notes (in thousands) Contractual interest expense $ 224 $ 1,617 $ 2,372 $ 3,310 $ 1,239 $ 404 $ 1,617 $ 1,031 Interest cost related to amortization of the debt discount 2,970 7,172 8,759 2,632 6,937 5,058 6,613 3,799 Total interest expense $ 3,194 $ 8,789 $ 11,131 $ 5,942 $ 8,176 $ 5,462 $ 8,230 $ 4,830 Nine Months Ended September 30, 2020 2019 2017 Notes 2018 Notes 2019 Notes 2020 Accreting Notes 2020 Notes 2017 Notes 2018 Notes 2019 Notes (in thousands) Contractual interest expense $ 1,033 $ 4,852 $ 7,063 $ 6,502 $ 1,239 $ 1,213 $ 4,852 $ 1,031 Interest cost related to amortization of the debt discount 13,471 21,075 25,912 4,317 6,937 14,948 19,423 3,799 Total interest expense $ 14,504 $ 25,927 $ 32,975 $ 10,819 $ 8,176 $ 16,161 $ 24,275 $ 4,830

Earnings (Loss) per Share (Tabl

Earnings (Loss) per Share (Tables)	9 Months Ended
	Sep. 30, 2020
Earnings Per Share [Abstract]
Schedule of Calculation of Basic and Diluted Net Loss Per Share	The following table presents the calculation of basic and diluted earnings (loss) per share: Three months ended September 30, Nine months ended September 30, 2020 2019 2020 2019 (in thousands, except per share data) Numerator: Numerator for basic EPS - Net income (loss) $ 173,166 $ (272,035) $ 161,178 $ (654,362) Effect of dilutive securities: Interest expense associated with convertible debt instruments 9,136 — — — Numerator for diluted EPS - net income (loss) available to common stockholders after the effect of dilutive securities $ 182,302 $ (272,035) $ 161,178 $ (654,362) Denominator: Denominator for basic EPS - weighted-average number of shares of common stock outstanding 95,373 92,540 94,767 91,820 Effect of dilutive securities: Employee stock options 24 — 32 — Restricted stock units 4,123 — 3,222 — Convertible debt instruments 9,680 — — — Dilutive potential common shares 13,827 — 3,254 — Denominator for diluted EPS - adjusted weighted-average number of shares of common stock outstanding after the effect of dilutive securities 109,200 92,540 98,021 91,820 Basic earnings (loss) per share $ 1.82 $ (2.94) $ 1.70 $ (7.13) Diluted earnings (loss) per share $ 1.67 $ (2.94) $ 1.64 $ (7.13)
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share	The potential common shares from anti-dilutive securities excluded from the weighted-average shares of common stock used to calculate diluted earnings (loss) per share were as follows: Three months ended September 30, Nine months ended September 30, 2020 2019 2020 2019 (in thousands) Outstanding employee stock options — 51 — 51 Unvested restricted common stock — 20 — 20 Unvested restricted stock units 116 7,823 510 7,823 Shares related to convertible debt instruments 13,228 15,474 20,232 15,474 Total 13,344 23,368 20,742 23,368
Shares Issued at Conversion and Capped Call Transactions	The number of shares of the Company's Class A common stock potentially issuable and obtainable at the respective conversion prices of the Notes and the Capped Call Transactions, respectively, by year, are as follows: 2017 Notes / Restated 2017 Capped Call Transactions 2018 Notes / 2018 Capped Call Transactions 2019 Notes / 2019 Capped Call Transactions 2020 Accreting Notes 2020 Notes / 2020 Capped Call Transactions (in thousands) Shares potentially issuable from convertible debt instruments 261 4,940 6,390 7,379 3,639 Shares obtainable from the exercise of capped call transactions (1,347) (2,322) (3,003) — (1,710) Total (1,086) 2,618 3,387 7,379 1,929

Description of Business (Detail

Description of Business (Details) supplier in Thousands, product in Millions	9 Months Ended
	Sep. 30, 2020supplierproduct
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of products offered | product	18
Number of suppliers providing products offered | supplier	12

Summary of Significant Accoun_3

Summary of Significant Accounting Policies - Adoption of ASU 2016-13 (Details) - USD ($) $ in Thousands	Jan. 01, 2020	Sep. 30, 2020	Jun. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Adoption of ASU, cumulative adjustment		$ 1,459,586	$ 787,392	$ 944,208	$ 682,429	$ 605,357	$ 330,721
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201613Member
Accumulated Deficit
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Adoption of ASU, cumulative adjustment		$ 1,909,768	$ 2,082,934	2,065,423	$ 1,735,201	$ 1,463,166	1,082,689
Cumulative Effect, Period of Adoption, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Adoption of ASU, cumulative adjustment				5,523			(1,850)
Cumulative Effect, Period of Adoption, Adjustment | Accumulated Deficit
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Adoption of ASU, cumulative adjustment				$ 5,523			$ (1,850)

Investments and Fair Value Me_3

Investments and Fair Value Measurements - Narrative (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Estimated fair values	$ 113,985,000		$ 113,985,000		$ 559,942,000
Credit losses recognized	0	$ 0	0	$ 0
Allowance for credit losses	0		0		0
Realized gains or losses	$ 0	$ 0	800,000	$ 0
Other long-term investments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Estimated fair values					$ 155,690,000
Proceeds from sale of investments			$ 161,300,000

Investments and Fair Value Me_4

Investments and Fair Value Measurements - Schedule of Marketable Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Marketable securities and fair value measurements
Amortized Cost	$ 113,886	$ 559,910
Gross Unrealized Gains	99	112
Gross Unrealized Losses	0	(80)
Estimated Fair Value	113,985	559,942
Short-term Investment securities
Marketable securities and fair value measurements
Amortized Cost	113,886	404,294
Gross Unrealized Gains	99	20
Gross Unrealized Losses	0	(62)
Estimated Fair Value	$ 113,985	404,252
Long-term Investment securities
Marketable securities and fair value measurements
Amortized Cost		155,616
Gross Unrealized Gains		92
Gross Unrealized Losses		(18)
Estimated Fair Value		$ 155,690

Investments and Fair Value Me_5

Investments and Fair Value Measurements - Schedule of Financial Assets Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Fair Value Assets Measured on Recurring and Nonrecurring Basis [line items]
Cash and cash equivalents	$ 2,442,939	$ 582,753
Total	2,562,124	1,147,771
Level 1
Fair Value Assets Measured on Recurring and Nonrecurring Basis [line items]
Cash and cash equivalents	2,442,939	582,753
Total	2,448,139	587,829
Level 2
Fair Value Assets Measured on Recurring and Nonrecurring Basis [line items]
Cash and cash equivalents	0	0
Total	113,985	559,942
Level 3
Fair Value Assets Measured on Recurring and Nonrecurring Basis [line items]
Cash and cash equivalents	0	0
Total	0	0
Investment securities
Fair Value Assets Measured on Recurring and Nonrecurring Basis [line items]
Short-term investments	113,985	404,252
Long-term investments		155,690
Investment securities | Level 1
Fair Value Assets Measured on Recurring and Nonrecurring Basis [line items]
Short-term investments	0	0
Long-term investments		0
Investment securities | Level 2
Fair Value Assets Measured on Recurring and Nonrecurring Basis [line items]
Short-term investments	113,985	404,252
Long-term investments		155,690
Investment securities | Level 3
Fair Value Assets Measured on Recurring and Nonrecurring Basis [line items]
Short-term investments	0	0
Long-term investments		0
Certificate of deposit
Fair Value Assets Measured on Recurring and Nonrecurring Basis [line items]
Other non-current assets	5,200	5,076
Certificate of deposit | Level 1
Fair Value Assets Measured on Recurring and Nonrecurring Basis [line items]
Other non-current assets	5,200	5,076
Certificate of deposit | Level 2
Fair Value Assets Measured on Recurring and Nonrecurring Basis [line items]
Other non-current assets	0	0
Certificate of deposit | Level 3
Fair Value Assets Measured on Recurring and Nonrecurring Basis [line items]
Other non-current assets	0	0
Cash
Fair Value Assets Measured on Recurring and Nonrecurring Basis [line items]
Cash and cash equivalents	538,767	308,521
Cash | Level 1
Fair Value Assets Measured on Recurring and Nonrecurring Basis [line items]
Cash and cash equivalents	538,767	308,521
Cash | Level 2
Fair Value Assets Measured on Recurring and Nonrecurring Basis [line items]
Cash and cash equivalents	0	0
Cash | Level 3
Fair Value Assets Measured on Recurring and Nonrecurring Basis [line items]
Cash and cash equivalents	0	0
Cash equivalents
Fair Value Assets Measured on Recurring and Nonrecurring Basis [line items]
Cash and cash equivalents	1,904,172	274,232
Cash equivalents | Level 1
Fair Value Assets Measured on Recurring and Nonrecurring Basis [line items]
Cash and cash equivalents	1,904,172	274,232
Cash equivalents | Level 2
Fair Value Assets Measured on Recurring and Nonrecurring Basis [line items]
Cash and cash equivalents	0	0
Cash equivalents | Level 3
Fair Value Assets Measured on Recurring and Nonrecurring Basis [line items]
Cash and cash equivalents	$ 0	$ 0

Credit Losses (Details)

Credit Losses (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2020	Dec. 31, 2019
Credit Loss [Abstract]
Revenue recognized, percent collected	99.00%	99.00%
Accounts receivable, net of allowance for credit losses	$ 109,652	$ 109,652	$ 99,720
Accounts receivable allowance for credit losses	$ 26,884	$ 26,884	$ 22,774

Intangible Assets and Goodwill

Intangible Assets and Goodwill (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible assets	$ 17.2		$ 17.2		$ 18.4
Amortization expense related to intangibles	0.4	$ 0.1	1.2	$ 0.4
Goodwill	$ 0.4		$ 0.4		$ 0.4

Property and Equipment, net (De

Property and Equipment, net (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Property and equipment, net
Property and equipment, gross	$ 1,316,528		$ 1,316,528		$ 1,080,389
Less accumulated depreciation and amortization	(634,471)		(634,471)		(455,845)
Property and equipment, net	682,057		682,057		624,544
Depreciation and amortization	72,200	$ 50,100	207,300	$ 133,800
Furniture and computer equipment
Property and equipment, net
Property and equipment, gross	554,489		554,489		509,120
Site and software development costs
Property and equipment, net
Property and equipment, gross	397,027		397,027		297,252
Leasehold improvements
Property and equipment, net
Property and equipment, gross	341,345		341,345		228,514
Construction in progress
Property and equipment, net
Property and equipment, gross	$ 23,667		$ 23,667		$ 45,503

Leases - Narrative (Details)

Leases - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Lessee, Lease, Description [Line Items]
Operating lease expense	$ 38.6	$ 31.8	$ 118.8	$ 86.8
Operating leases not yet commenced			$ 149.4
Minimum
Lessee, Lease, Description [Line Items]
Operating leases not yet commenced, term of contract	2 years		2 years
Maximum
Lessee, Lease, Description [Line Items]
Operating leases not yet commenced, term of contract	15 years		15 years

Leases - Other Information Rela

Leases - Other Information Related to Leases (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Supplemental cash flows information
Cash payments included in operating cash flows from lease arrangements	$ 105,416	$ 77,687
Right-of-use assets obtained in exchange for lease obligations	$ 110,210	$ 281,006
Additional lease information
Weighted average remaining lease term	8 years		10 years
Weighted average discount rate	6.50%		6.70%

Leases - Future Minimum Lease P

Leases - Future Minimum Lease Payments (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Leases [Abstract]
2020 (excluding the nine months ended September 30, 2020)	$ 33,793
2021	161,998
2022	162,800
2023	157,581
2024	155,062
Thereafter	602,837
Total future minimum lease payments	1,274,071
Less: Imputed interest	(303,994)
Total	$ 970,077	$ 913,706

Leases - Operating Leases Balan

Leases - Operating Leases Balance Sheet Locations (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Leases [Abstract]
Other current liabilities	$ 102,366	$ 91,104
Operating lease liabilities	867,711	822,602
Total operating leases	$ 970,077	$ 913,706
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:OtherLiabilitiesCurrent	us-gaap:OtherLiabilitiesCurrent

Commitments and Contingencies (

Commitments and Contingencies (Details) $ in Millions	Jan. 16, 2019officerplaintiff	Sep. 30, 2020USD ($)	Dec. 31, 2019USD ($)
Commitments and Contingencies Disclosure [Abstract]
Letter of credit issued as security for lease agreements | $		$ 54.9	$ 46.7
Number of Company's officers | officer	3
Number of plaintiffs | plaintiff	2

Equity-Based Compensation - Nar

Equity-Based Compensation - Narrative (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Jan. 01, 2020
Employee stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Intrinsic value of stock options exercised	$ 4.4	$ 4.2
Aggregate intrinsic value of stock options outstanding	5.7
Aggregate intrinsic value of stock options exercisable	5.7
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Intrinsic value of stock vested	342.9	$ 290.5
Aggregate intrinsic value of stock unvested	1,800
Unrecognized equity-based compensation	$ 649.7
Weighted average remaining vesting term	1 year 2 months 12 days
2014 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized (in shares)	8,603,066
Number of shares available for future grant (in shares)			5,111,305

Equity-Based Compensation - Sum

Equity-Based Compensation - Summary of Activity Relating to Stock Options (Details) - Employee stock options - $ / shares	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Shares
Outstanding at the beginning of the period (in shares)	43,606
Options exercised (in shares)	(23,660)
Outstanding and exercisable at the end of the period (in shares)	19,946	43,606
Weighted-Average Exercise Price
Outstanding at the beginning of the period (in dollars per share)	$ 3
Options exercised (in dollars per share)	3.02
Outstanding and exercisable at the end of the period (in dollars per share)	$ 2.98	$ 3
Weighted-Average Remaining Contractual Term (Years)
Outstanding	8 months 12 days	1 year 6 months

Equity-Based Compensation - S_2

Equity-Based Compensation - Summary of Activity Relating to Restricted Stock (Details) - RSUs	9 Months Ended
	Sep. 30, 2020$ / sharesshares
Shares
Outstanding at the beginning of the period (in shares) | shares	8,112,736
RSUs granted (in shares) | shares	1,688,442
RSUs vested (in shares) | shares	(2,233,708)
RSUs forfeited/canceled (in shares) | shares	(1,343,119)
Outstanding at the end of the period (in shares) | shares	6,224,351
Weighted- Average Grant Date Fair Value
Outstanding at the beginning of the period (in dollars per share) | $ / shares	$ 95.69
RSUs granted (in dollars per share) | $ / shares	171.72
RSUs vested (in dollars per share) | $ / shares	95.30
RSUs forfeited/canceled (in dollars per share) | $ / shares	103.73
Outstanding at the end of the period (in dollars per share) | $ / shares	$ 115.27

Unearned Revenue (Details)

Unearned Revenue (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Unearned revenue
Disaggregation of Revenue [Line Items]
Contract liabilities	$ 318.2	$ 167.6
Revenue recognized that was included in deferred revenue	139.7
Other current liabilities
Disaggregation of Revenue [Line Items]
Contract liabilities	5.3	$ 4.6
Revenue recognized that was included in deferred revenue	$ 2.8

Segment and Geographic Inform_3

Segment and Geographic Information - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting Information [Line Items]
Net revenue	$ 3,839,570	$ 2,305,487	$ 10,474,305	$ 6,593,567
U.S.
Segment Reporting Information [Line Items]
Net revenue	$ 3,274,872	1,966,654	$ 8,901,559	5,624,870
U.S. | Other
Segment Reporting Information [Line Items]
Net revenue		$ (5,800)		$ (30,900)

Segment and Geographic Inform_4

Segment and Geographic Information - Activity Related to Net Revenue and Adjusted EBITDA (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting Information [Line Items]
Net revenue	$ 3,839,570	$ 2,305,487	$ 10,474,305	$ 6,593,567
Adjusted EBITDA	371,112	(144,184)	683,648	(316,385)
Less: reconciling items	(197,946)	(127,851)	(522,470)	(337,977)
Net income (loss)	173,166	(272,035)	161,178	(654,362)
Depreciation and amortization	72,575	50,250	208,532	134,172
Equity-based compensation and related taxes	76,683	65,275	211,376	173,963
Interest expense, net	36,315	14,432	87,472	33,922
Other expense (income), net	13,584	(2,182)	10,720	(5,582)
(Benefit) provision for income taxes, net	(1,211)	76	414	1,502
Other	0	0	3,956	0
Less: reconciling items	197,946	127,851	522,470	337,977
Segment Reconciling Items
Segment Reporting Information [Line Items]
Adjusted EBITDA	(197,946)	(127,851)	(522,470)	(337,977)
U.S.
Segment Reporting Information [Line Items]
Net revenue	3,274,872	1,966,654	8,901,559	5,624,870
U.S. | Operating Segments
Segment Reporting Information [Line Items]
Adjusted EBITDA	377,007	(62,878)	766,486	(91,002)
International
Segment Reporting Information [Line Items]
Net revenue	564,698	338,833	1,572,746	968,697
International | Operating Segments
Segment Reporting Information [Line Items]
Adjusted EBITDA	$ (5,895)	$ (81,306)	$ (82,838)	$ (225,383)

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Income Tax Disclosure [Abstract]
(Benefit) provision for income taxes, net	$ (1,211)	$ 76	$ 414	$ 1,502
Unrecognized tax benefits	$ 0		$ 0		$ 0

Stockholders' Deficit (Details)

Stockholders' Deficit (Details)	3 Months Ended	9 Months Ended		72 Months Ended
	Sep. 30, 2020USD ($)$ / sharesshares	Sep. 30, 2020USD ($)vote$ / sharesshares	Sep. 30, 2019USD ($)	Sep. 30, 2020$ / sharesshares	Aug. 21, 2020USD ($)	Dec. 31, 2019$ / sharesshares	Dec. 31, 2018USD ($)
Stockholders' Equity
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000		10,000,000
Preferred stock, par value (in dollars per share) | $ / shares	$ 0.001	$ 0.001		$ 0.001
Preferred stock, shares issued (in shares)	0	0		0
Preferred stock, shares outstanding (in shares)	0	0		0
Stock repurchase program, authorized amount | $					$ 700,000,000		$ 200,000,000
Repurchase of common stock | $	$ (280,200,000)	$ (280,236,000)	$ 0
Stock repurchase program, average repurchase price per share (USD per share) | $ / shares	$ 331.65	$ 331.65
Class A common stock
Stockholders' Equity
Common stock, shares authorized (in shares)	500,000,000	500,000,000		500,000,000		500,000,000
Common stock, par value (in dollars per share) | $ / shares	$ 0.001	$ 0.001		$ 0.001		$ 0.001
Common stock, shares outstanding (in shares)	68,959,957	68,959,957		68,959,957		66,642,611
Number of votes each holder is entitled | vote		1
Class B common stock
Stockholders' Equity
Common stock, shares authorized (in shares)	164,000,000	164,000,000		164,000,000		164,000,000
Common stock, par value (in dollars per share) | $ / shares	$ 0.001	$ 0.001		$ 0.001		$ 0.001
Common stock, shares outstanding (in shares)	26,636,721	26,636,721		26,636,721		26,957,815
Number of votes each holder is entitled | vote		10
Conversion ratio following the completion of the offering		1
Conversion ratio upon transfer		1
Number of shares converted into Class A common stock (in shares)				55,401,693
Class B common stock | Maximum
Stockholders' Equity
Aggregate number of shares outstanding Class A common stock and Class B common stock that shall convert automatically (less than)		10.00%
Class B common stock | Minimum
Stockholders' Equity
Percentage of outstanding shares of Class B common stock that shall convert automatically in the event of the affirmative vote or written consent of holders		66.67%

Credit Agreement (Details)

Credit Agreement (Details) - USD ($)	Oct. 30, 2020	Sep. 30, 2020	Dec. 31, 2019
Line of Credit Facility [Line Items]
Long-term debt		$ 2,862,135,000	$ 1,456,195,000
Revolving Credit Facility | Senior Secured Revolving Credit Facility
Line of Credit Facility [Line Items]
Maximum borrowing capacity		200,000,000
Long-term debt		$ 0
Revolving Credit Facility | Revolving Loan Commitments | Subsequent Event
Line of Credit Facility [Line Items]
Maximum borrowing capacity	$ 200,000,000

Convertible Debt - Narrative (D

Convertible Debt - Narrative (Details)	Aug. 14, 2020USD ($)day$ / shares	Aug. 11, 2020$ / shares	Apr. 08, 2020USD ($)day$ / shares	Aug. 19, 2019USD ($)day$ / shares	Aug. 14, 2019$ / shares	Nov. 19, 2018USD ($)day$ / shares	Nov. 14, 2018$ / shares	Sep. 15, 2017USD ($)day$ / shares	Sep. 11, 2017institution$ / shares	Oct. 31, 2020USD ($)shares	Aug. 31, 2020USD ($)	Nov. 30, 2018USD ($)	Sep. 30, 2020USD ($)shares	Sep. 30, 2019USD ($)	Sep. 30, 2020USD ($)	Sep. 30, 2019USD ($)	Dec. 31, 2019USD ($)
Debt Instrument [Line Items]
Over-allotment option included in issuance of notes															$ 2,027,758,000	$ 935,146,000
Number of initial purchasers | institution									2
Proceeds from sale of Notes, net of discounts and offering expenses											$ 1,000,000,000
Premiums paid for capped call confirmations															255,024,000	145,728,000
Beneficial conversion feature of notes													$ 39,374,000	$ 130,566,000	78,263,000	$ 130,566,000
Carrying value of debt													2,862,135,000		2,862,135,000		$ 1,456,195,000
2020 Accreting Notes
Debt Instrument [Line Items]
Effective interest rate			4.40%
Beneficial conversion feature of notes			$ 39,400,000
2020 Accreting Notes | Director
Debt Instrument [Line Items]
Debt, aggregate principal			$ 535,000,000
Convertible Debt | 0.375% 2017 Senior Notes due 2022
Debt Instrument [Line Items]
Debt, aggregate principal								$ 431,250,000					27,171,000		27,171,000		431,250,000
Interest rate, stated percentage								0.375%
Initial conversion rate								0.00961
Conversion price (in usd per share) | $ / shares								$ 104.06
Number of trading days (whether or not consecutive) | day								20
Number of trading days (consecutive) | day								30
Percentage of conversion stock price								130.00%
During number of business day period								5 days
Consecutive trading day period (after any)								10 days
Principal amount of Notes								$ 1,000
Measurement period, percentage (less than)								98.00%
Minimum trading days immediately preceding date notice of redemption provided | day								1
Trading days immediately preceding date notice of redemption provided | day								5
Redemption price, percentage of principal amount to be redeemed								100.00%
Default percentage of aggregate principal amount of notes outstanding (not less than)								25.00%
Proceeds from sale of Notes, net of discounts and offering expenses								$ 420,400,000
Premiums paid for capped call confirmations								44,200,000
Equity component of Notes								95,800,000
Aggregate principal amount of repurchased Notes											343,400,000
Debt conversion, principal amount													$ 60,600,000
Debt conversion, converted, shares issued (in shares) | shares													582,825
Loss on debt repurchase											(12,600,000)
Carrying value of debt											360,500,000		$ 24,407,000		24,407,000		371,420,000
Debt repurchase amount, portion allocated to equity component											818,700,000
Debt, fair value													75,600,000		75,600,000
Convertible debt, if-converted value in excess of principal															48,800,000
Convertible Debt | 0.375% 2017 Senior Notes due 2022 | Class A common stock
Debt Instrument [Line Items]
Cap price, per share (in usd per share) | $ / shares									$ 154.16
Premium over last reported sale price, percentage									100.00%
Convertible Debt | 0.375% 2017 Senior Notes due 2022 | Over-Allotment Option
Debt Instrument [Line Items]
Over-allotment option included in issuance of notes								$ 56,250,000
Effective interest rate								6.00%
Convertible Debt | 1.125% 2018 Senior Notes Due 2024
Debt Instrument [Line Items]
Debt, aggregate principal						$ 500,000,000						$ 575,000,000	575,000,000		575,000,000		575,000,000
Interest rate, stated percentage												1.125%
Over-allotment option included in issuance of notes						$ 75,000,000						$ 75,000,000
Initial conversion rate						0.008591
Number of trading days (whether or not consecutive) | day						20
Number of trading days (consecutive) | day						30
Percentage of conversion stock price						130.00%
During number of business day period						5 days
Consecutive trading day period (after any)						10 days
Principal amount of Notes						$ 1,000
Measurement period, percentage (less than)						98.00%
Minimum trading days immediately preceding date notice of redemption provided | day						1
Trading days immediately preceding date notice of redemption provided | day						5
Redemption price, percentage of principal amount to be redeemed						100.00%
Default percentage of aggregate principal amount of notes outstanding (not less than)						25.00%
Proceeds from sale of Notes, net of discounts and offering expenses												562,000,000
Premiums paid for capped call confirmations												$ 93,400,000
Effective interest rate												8.10%
Equity component of Notes												$ 181,500,000
Carrying value of debt													434,800,000		434,800,000		413,725,000
Debt, fair value													1,500,000,000		1,500,000,000
Convertible debt, if-converted value in excess of principal															862,500,000
Convertible Debt | 1.125% 2018 Senior Notes Due 2024 | Class A common stock
Debt Instrument [Line Items]
Interest rate, stated percentage						1.125%
Conversion price (in usd per share) | $ / shares						$ 116.40
Cap price, per share (in usd per share) | $ / shares							$ 219.63
Premium over last reported sale price, percentage							150.00%
Convertible Debt | 1.00% 2019 Senior Notes Due 2026
Debt Instrument [Line Items]
Debt, aggregate principal				$ 948,750,000									948,750,000		948,750,000		948,750,000
Interest rate, stated percentage				1.00%
Over-allotment option included in issuance of notes				$ 123,750,000
Initial conversion rate				0.0067349
Number of trading days (consecutive) | day				30
Percentage of conversion stock price				130.00%
During number of business day period				5 days
Consecutive trading day period (after any)				10 days
Principal amount of Notes				$ 1,000
Measurement period, percentage (less than)				98.00%
Redemption price, percentage of principal amount to be redeemed				100.00%
Default percentage of aggregate principal amount of notes outstanding (not less than)				25.00%
Proceeds from sale of Notes, net of discounts and offering expenses				$ 935,100,000
Premiums paid for capped call confirmations				$ 145,700,000
Effective interest rate				6.40%
Equity component of Notes				$ 280,300,000
Carrying value of debt													697,202,000		697,202,000		$ 671,050,000
Debt, fair value													1,800,000,000		1,800,000,000
Convertible debt, if-converted value in excess of principal															910,700,000
Convertible Debt | 1.00% 2019 Senior Notes Due 2026 | Class A common stock
Debt Instrument [Line Items]
Interest rate, stated percentage				1.00%
Conversion price (in usd per share) | $ / shares				$ 148.48
Number of trading days (whether or not consecutive) | day				20
Number of trading days (consecutive) | day				30
Cap price, per share (in usd per share) | $ / shares					$ 280.15
Premium over last reported sale price, percentage					150.00%
Convertible Debt | 2020 Notes
Debt Instrument [Line Items]
Debt, aggregate principal	$ 1,518,000,000												1,518,000,000		1,518,000,000
Interest rate, stated percentage	0.625%
Over-allotment option included in issuance of notes	$ 198,000,000
Initial conversion rate	0.0023972
Conversion price (in usd per share) | $ / shares	$ 417.15
Number of trading days (whether or not consecutive) | day	20
Number of trading days (consecutive) | day	30
Percentage of conversion stock price	130.00%
During number of business day period	5 days
Consecutive trading day period (after any)	10 days
Principal amount of Notes	$ 1,000
Measurement period, percentage (less than)	98.00%
Redemption price, percentage of principal amount to be redeemed	100.00%
Default percentage of aggregate principal amount of notes outstanding (not less than)	25.00%
Proceeds from sale of Notes, net of discounts and offering expenses	$ 1,500,000,000
Premiums paid for capped call confirmations	$ 255,000,000
Effective interest rate	5.20%
Equity component of Notes	$ 297,400,000
Debt repurchase amount, portion allocated to debt component											$ 371,800,000
Carrying value of debt													1,213,376,000		1,213,376,000
Debt, fair value													1,500,000,000		1,500,000,000
Convertible Debt | 2020 Notes | Class A common stock
Debt Instrument [Line Items]
Cap price, per share (in usd per share) | $ / shares		$ 787.08
Premium over last reported sale price, percentage		150.00%
Convertible Debt | 2020 Accreting Notes
Debt Instrument [Line Items]
Debt, aggregate principal													535,000,000		535,000,000
Interest rate, stated percentage			2.50%
Conversion price (in usd per share) | $ / shares			$ 72.50
Number of trading days (whether or not consecutive) | day			20
Number of trading days (consecutive) | day			30
Percentage of conversion stock price			276.00%
Principal amount of Notes			$ 1,000
Redemption price, percentage of principal amount to be redeemed			100.00%
Default percentage of aggregate principal amount of notes outstanding (not less than)			25.00%
Carrying value of debt													492,350,000		492,350,000
Debt, fair value													$ 2,200,000,000		2,200,000,000
Convertible debt, if-converted value in excess of principal															$ 1,600,000,000
Convertible Debt | 2020 Accreting Notes | Subsequent Event
Debt Instrument [Line Items]
Debt conversion, principal amount										$ 253,100,000
Debt conversion, converted, shares issued (in shares) | shares										3,490,175
Convertible Debt | 2020 Accreting Notes | Director
Debt Instrument [Line Items]
Debt, aggregate principal			$ 535,000,000
Proceeds from sale of Notes, net of discounts and offering expenses			$ 527,400,000

Convertible Debt - Schedule of

Convertible Debt - Schedule of Outstanding Principal Amount and Carrying Value of Notes (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Aug. 31, 2020	Aug. 14, 2020	Dec. 31, 2019	Aug. 19, 2019	Nov. 30, 2018	Nov. 19, 2018	Sep. 15, 2017
Debt Instrument [Line Items]
Net carrying amount	$ 2,862,135,000		$ 2,862,135,000				$ 1,456,195,000
Convertible Debt | 2017 Notes
Debt Instrument [Line Items]
Principal	27,171,000		27,171,000				431,250,000				$ 431,250,000
Unamortized debt discount	(2,764,000)		(2,764,000)				(59,830,000)
Net carrying amount	24,407,000		24,407,000		$ 360,500,000		371,420,000
Contractual interest expense	224,000	$ 404,000	1,033,000	$ 1,213,000
Interest cost related to amortization of the debt discount	2,970,000	5,058,000	13,471,000	14,948,000
Interest Expense	3,194,000	5,462,000	14,504,000	16,161,000
Convertible Debt | 2018 Notes
Debt Instrument [Line Items]
Principal	575,000,000		575,000,000				575,000,000		$ 575,000,000	$ 500,000,000
Unamortized debt discount	(140,200,000)		(140,200,000)				(161,275,000)
Net carrying amount	434,800,000		434,800,000				413,725,000
Contractual interest expense	1,617,000	1,617,000	4,852,000	4,852,000
Interest cost related to amortization of the debt discount	7,172,000	6,613,000	21,075,000	19,423,000
Interest Expense	8,789,000	8,230,000	25,927,000	24,275,000
Convertible Debt | 2019 Notes
Debt Instrument [Line Items]
Principal	948,750,000		948,750,000				948,750,000	$ 948,750,000
Unamortized debt discount	(251,548,000)		(251,548,000)				(277,700,000)
Net carrying amount	697,202,000		697,202,000				$ 671,050,000
Contractual interest expense	2,372,000	1,031,000	7,063,000	1,031,000
Interest cost related to amortization of the debt discount	8,759,000	3,799,000	25,912,000	3,799,000
Interest Expense	11,131,000	$ 4,830,000	32,975,000	$ 4,830,000
Convertible Debt | 2020 Accreting Notes
Debt Instrument [Line Items]
Principal	535,000,000		535,000,000
Unamortized debt discount	(42,650,000)		(42,650,000)
Net carrying amount	492,350,000		492,350,000
Contractual interest expense	3,310,000		6,502,000
Interest cost related to amortization of the debt discount	2,632,000		4,317,000
Interest Expense	5,942,000		10,819,000
Convertible Debt | 2020 Notes
Debt Instrument [Line Items]
Principal	1,518,000,000		1,518,000,000			$ 1,518,000,000
Unamortized debt discount	(304,624,000)		(304,624,000)
Net carrying amount	1,213,376,000		1,213,376,000
Contractual interest expense	1,239,000		1,239,000
Interest cost related to amortization of the debt discount	6,937,000		6,937,000
Interest Expense	$ 8,176,000		$ 8,176,000

Convertible Debt - Schedule o_2

Convertible Debt - Schedule of Interest Expense Related to Notes (Details) - Convertible Debt - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
2017 Notes
Debt Instrument [Line Items]
Contractual interest expense	$ 224	$ 404	$ 1,033	$ 1,213
Interest cost related to amortization of the debt discount	2,970	5,058	13,471	14,948
Total interest expense	3,194	5,462	14,504	16,161
2018 Notes
Debt Instrument [Line Items]
Contractual interest expense	1,617	1,617	4,852	4,852
Interest cost related to amortization of the debt discount	7,172	6,613	21,075	19,423
Total interest expense	8,789	8,230	25,927	24,275
2019 Notes
Debt Instrument [Line Items]
Contractual interest expense	2,372	1,031	7,063	1,031
Interest cost related to amortization of the debt discount	8,759	3,799	25,912	3,799
Total interest expense	11,131	$ 4,830	32,975	$ 4,830
2020 Accreting Notes
Debt Instrument [Line Items]
Contractual interest expense	3,310		6,502
Interest cost related to amortization of the debt discount	2,632		4,317
Total interest expense	5,942		10,819
2020 Notes
Debt Instrument [Line Items]
Contractual interest expense	1,239		1,239
Interest cost related to amortization of the debt discount	6,937		6,937
Total interest expense	$ 8,176		$ 8,176

Earnings (Loss) per Share - Nar

Earnings (Loss) per Share - Narrative (Details)	9 Months Ended
	Sep. 30, 2020
Earnings Per Share [Abstract]
Allocation of undistributed earnings between stock classes, conversion ratio	1

Earnings (Loss) per Share - Cal

Earnings (Loss) per Share - Calculation of Basic and Diluted Earnings (Loss ) Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Numerator:
Numerator for basic EPS - Net income (loss)	$ 173,166	$ (272,035)	$ 161,178	$ (654,362)
Effect of dilutive securities
Interest expense associated with convertible debt instruments	9,136	0	0	0
Numerator for diluted EPS - net income (loss) available to common stockholders after the effect of dilutive securities	$ 182,302	$ (272,035)	$ 161,178	$ (654,362)
Denominator:
Denominator for basic EPS - weighted average number of shares of common stock outstanding (in shares)	95,373	92,540	94,767	91,820
Effect of dilutive securities:
Convertible debt instruments (in shares)	9,680	0	0	0
Dilutive potential common shares (in shares)	13,827	0	3,254	0
Denominator for diluted EPS - adjusted weighted-average number of shares of common stock outstanding after the effect of dilutive securities (in shares)	109,200	92,540	98,021	91,820
Basic earnings (loss) per share (in usd per share)	$ 1.82	$ (2.94)	$ 1.70	$ (7.13)
Diluted earnings (loss) per share (in usd per share)	$ 1.67	$ (2.94)	$ 1.64	$ (7.13)
Employee stock options
Effect of dilutive securities:
Incremental common shares attributable to dilutive effect of share-based payment award (in shares)	24	0	32	0
Restricted stock units
Effect of dilutive securities:
Incremental common shares attributable to dilutive effect of share-based payment award (in shares)	4,123	0	3,222	0

Earnings (Loss) per Share - Ant

Earnings (Loss) per Share - Antidilutive Securities (Details) - shares shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from diluted earnings per share calculation (in shares)	13,344	23,368	20,742	23,368
Employee stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from diluted earnings per share calculation (in shares)	0	51	0	51
Restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from diluted earnings per share calculation (in shares)	0	20	0	20
RSUs
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from diluted earnings per share calculation (in shares)	116	7,823	510	7,823
Shares related to convertible debt instruments
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from diluted earnings per share calculation (in shares)	13,228	15,474	20,232	15,474

Earnings ( Loss) per Share - Sc

Earnings ( Loss) per Share - Schedule of Shares of Stock Potentially Issuable for Convertible Debt and Capped Call Transactions (Details) shares in Thousands	9 Months Ended
	Sep. 30, 2020shares
Convertible Debt
Class of Stock [Line Items]
Shares potentially issuable from convertible debt instruments (in shares)
2017 Notes | Convertible Debt
Class of Stock [Line Items]
Shares potentially issuable from convertible debt instruments (in shares)	261
2018 Notes | Convertible Debt
Class of Stock [Line Items]
Shares potentially issuable from convertible debt instruments (in shares)	4,940
2019 Notes | Convertible Debt
Class of Stock [Line Items]
Shares potentially issuable from convertible debt instruments (in shares)	6,390
2020 Accreting Notes
Class of Stock [Line Items]
Total	7,379
2020 Accreting Notes | Convertible Debt
Class of Stock [Line Items]
Shares potentially issuable from convertible debt instruments (in shares)	7,379
2020 Notes | Convertible Debt
Class of Stock [Line Items]
Shares potentially issuable from convertible debt instruments (in shares)	3,639
2017 Capped Call Transactions
Class of Stock [Line Items]
Shares obtainable from the exercise of capped call transactions (in shares)	(1,347)
2018 Capped Call Transactions
Class of Stock [Line Items]
Shares obtainable from the exercise of capped call transactions (in shares)	(2,322)
2019 Capped Call Transactions
Class of Stock [Line Items]
Shares obtainable from the exercise of capped call transactions (in shares)	(3,003)
2020 Capped Call Transactions
Class of Stock [Line Items]
Shares obtainable from the exercise of capped call transactions (in shares)	(1,710)
2017 Notes / Restated 2017 Capped Call Transactions
Class of Stock [Line Items]
Total	(1,086)
2018 Notes / 2018 Capped Call Transactions
Class of Stock [Line Items]
Total	2,618
2019 Notes / 2019 Capped Call Transactions
Class of Stock [Line Items]
Total	3,387
2020 Notes and 2020 Capped Call Transactions
Class of Stock [Line Items]
Total	1,929

Related Party Transactions (Det

Related Party Transactions (Details)	Apr. 08, 2020USD ($)
Director | 2020 Accreting Notes
Related Party Transaction [Line Items]
Debt, aggregate principal	$ 535,000,000