Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Operating activities
Net loss	$ (163,273)	$ (67,525)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation and amortization	29,026	20,525
Share-based compensation expense	43,795	66,124
Amortization of right of use assets	6,465	4,440
Amortization of contract cost assets	8,415	8,746
Amortization of discount and issuance costs on convertible senior notes maturing in 2021, 2023, 2024 and 2026	22,547	8,840
Impairment costs	76,800	0
Deferred income taxes	(9,228)	(2,500)
Loss on disposal of property and equipment and other assets	1,952	1,704
Credit loss expense	558	128
Net loss on investment securities	434	0
Accretion of bond discount	(473)	(1,733)
Changes in operating assets and liabilities:
Accounts receivable	(5,335)	(4,650)
Mortgage loans held for sale	(341)	5,940
Inventory	302,593	(162,325)
Prepaid expenses and other assets	(2,916)	(8,537)
Lease liabilities	(1,625)	(7,010)
Contract cost assets	(9,771)	(9,103)
Accounts payable	7,673	(133)
Accrued expenses and other current liabilities	4,588	328
Accrued compensation and benefits	(4,967)	(1,088)
Deferred revenue	(4,400)	2,025
Other long-term liabilities	(527)	290
Net cash provided by (used in) operating activities	301,990	(145,514)
Investing activities
Proceeds from maturities of investments	296,272	302,187
Proceeds from sales of investments	53,997	0
Purchases of investments	(58,459)	(176,412)
Purchases of property and equipment	(32,966)	(14,202)
Purchases of intangible assets	(4,503)	(3,269)
Net cash provided by investing activities	254,341	108,304
Financing activities
Proceeds from borrowings on credit facilities	34,460	129,328
Repayments of borrowings on credit facilities	(294,150)	0
Net borrowings (repayments) on warehouse lines of credit and repurchase agreement	4,386	(5,025)
Proceeds from exercise of stock options	92,202	13,564
Value of equity awards withheld for tax liability	0	2
Net cash provided by (used in) financing activities	(163,102)	137,869
Net increase in cash, cash equivalents and restricted cash during period	393,229	100,659
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	1,624,138	764,102
Supplemental disclosures of cash flow information
Cash paid for interest	17,038	4,956
Noncash transactions:
Capitalized share-based compensation	3,670	2,690
Write-off of fully depreciated property and equipment	4,143	6,269
Write-off of fully amortized intangible assets	0	3,200
Property and equipment purchased on account	$ 9,445	$ 4,792