Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Operating activities
Net loss	$ (247,721)	$ (139,502)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation and amortization	55,199	41,728
Share-based compensation expense	96,146	109,756
Amortization of right of use assets	12,731	10,572
Amortization of contract cost assets	17,070	17,880
Amortization of discount and issuance costs on convertible senior notes maturing in 2021, 2023, 2024, 2025 and 2026	47,746	17,799
Gain on partial extinguishment of 2021 Notes	(6,391)	0
Impairment costs	76,800	0
Deferred income taxes	(8,549)	(2,500)
(Gain) loss on disposal of property and equipment and other assets	(2,658)	3,878
Credit loss expense	1,614	706
Net loss on investment securities	372	0
Accretion of bond discount	(303)	(3,695)
Changes in operating assets and liabilities:
Accounts receivable	(1,487)	(16,884)
Mortgage loans held for sale	(38,514)	(3,244)
Inventory	701,145	(389,994)
Prepaid expenses and other assets	(771)	(2,015)
Lease liabilities	(495)	(11,946)
Contract cost assets	(19,608)	(18,332)
Accounts payable	7,504	1,256
Accrued expenses and other current liabilities	(8,741)	6,952
Accrued compensation and benefits	(3,285)	613
Deferred revenue	4,767	3,000
Other long-term liabilities	10,049	149
Net cash provided by (used in) operating activities	692,620	(373,823)
Investing activities
Proceeds from maturities of investments	701,266	539,312
Proceeds from sales of investments	116,394	0
Purchases of investments	(1,026,233)	(302,891)
Purchases of property and equipment	(54,653)	(29,672)
Purchases of intangible assets	(11,408)	(8,927)
Proceeds from sale of equity investment	10,000	0
Net cash provided by (used in) investing activities	(264,634)	197,822
Financing activities
Proceeds from issuance of 2025 Notes, net of issuance costs	553,282	0
Proceeds from Issuance of Common Stock	411,522	0
Partial extinguishment of 2021 Notes	(194,670)	0
Proceeds from borrowings on credit facilities	43,200	293,099
Repayments of borrowings on credit facilities	(617,506)	0
Net borrowings (repayments) on warehouse lines of credit and repurchase agreement	39,387	(2,961)
Proceeds from exercise of stock options	184,984	32,997
Value of equity awards withheld for tax liability	0	3
Net cash provided by financing activities	420,199	323,138
Net increase in cash, cash equivalents and restricted cash during period	848,185	147,137
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	2,079,094	810,580
Supplemental disclosures of cash flow information
Cash paid for interest	29,201	16,616
Noncash transactions:
Capitalized share-based compensation	8,490	5,878
Write-off of fully depreciated property and equipment	6,942	9,867
Write-off of fully amortized intangible assets	0	3,311
Property and equipment purchased on account	$ 5,305	$ 2,408