Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Operating activities
Net loss	$ (208,151)	$ (204,151)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation and amortization	81,977	63,888
Share-based compensation expense	145,105	151,884
Amortization of right of use assets	18,364	16,710
Amortization of contract cost assets	26,554	26,722
Amortization of discount and issuance costs on convertible senior notes maturing in 2021, 2023, 2024, 2025 and 2026	75,414	29,868
Gain on partial extinguishment of 2021 Notes	(6,391)	0
Impairment costs	76,800	0
Deferred income taxes	(8,124)	(3,800)
Loss (gain) on disposal of property and equipment and other assets	(1,032)	5,755
Credit loss expense	1,846	1,894
Net loss (gain) on investment securities	372	(11)
Accretion of bond discount	(238)	(5,241)
Changes in operating assets and liabilities:
Accounts receivable	(14,483)	(13,485)
Mortgage loans held for sale	(88,817)	(1,353)
Inventory	643,265	(716,524)
Prepaid expenses and other assets	(16,385)	(5,848)
Contract cost assets	(31,833)	(26,950)
Lease liabilities	4,773	(15,029)
Accounts payable	12,239	2,999
Accrued expenses and other current liabilities	14,499	12,241
Accrued compensation and benefits	(2,331)	2,152
Deferred revenue	9,406	7,875
Other long-term liabilities	17,329	122
Net cash provided by (used in) operating activities	750,158	(670,282)
Investing activities
Proceeds from maturities of investments	1,160,271	859,142
Proceeds from sales of investments	116,394	0
Purchases of investments	(1,881,002)	(479,963)
Purchases of property and equipment	(72,420)	(45,140)
Purchases of intangible assets	(17,226)	(15,123)
Proceeds from sale of equity investment	10,000	0
Net cash provided by (used in) investing activities	(683,983)	318,916
Financing activities
Proceeds from issuance of convertible notes, net of issuance costs	553,282	1,085,686
Premiums paid for capped call confirmations	0	(150,530)
Proceeds from Issuance of Common Stock	411,522	0
Partial extinguishment of 2021 Notes	(194,670)	0
Proceeds from borrowings on credit facilities	97,437	581,580
Repayments of borrowings on credit facilities	(674,658)	0
Net borrowings (repayments) on warehouse lines of credit and repurchase agreement	87,667	(2,902)
Proceeds from exercise of stock options	371,226	41,014
Value of equity awards withheld for tax liability	(2)	(3)
Net cash provided by financing activities	651,804	1,554,845
Net increase in cash, cash equivalents and restricted cash during period	717,979	1,203,479
Cash, cash equivalents and restricted cash at beginning of period	1,230,909	663,443
Cash, cash equivalents and restricted cash at end of period	1,948,888	1,866,922
Supplemental disclosures of cash flow information
Cash paid for interest	36,787	25,837
Noncash transactions:
Capitalized share-based compensation	13,020	8,942
Write-off of fully depreciated property and equipment	13,100	28,951
Write-off of fully amortized intangible assets	0	9,959
Property and equipment purchased on account	$ 1,645	$ 4,606