Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Operating Activities
Net loss	$ (35,784)	$ (60,117)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	4,341	3,307
Stock-based compensation	12,583	7,211
Amortization of debt discount and issuance costs	855	1,730
Non-cash lease expense	2,533	2,254
Impairment costs	0	1,420
Net gain on IRLCs, forward sales commitments and loans held for sale	(1,052)	(494)
Other	109	(119)
Change in assets and liabilities:
Accounts receivable, net	7,303	(2,598)
Inventory	(48,213)	3,941
Prepaid expenses and other assets	(3,359)	4,934
Accounts payable	5,947	514
Accrued liabilities, other payables, and payroll tax liabilities, noncurrent	8,873	18,725
Lease liabilities	(2,951)	(2,693)
Origination of loans held for sale	(227,090)	(132,697)
Proceeds from sale of loans originated as held for sale	225,140	111,233
Net cash used in operating activities	(50,765)	(43,449)
Investing activities
Purchases of property and equipment	(5,285)	(3,406)
Purchases of investments	(67,877)	(33,267)
Sales of investments	0	31,608
Maturities of investments	63,589	1,597
Net cash used in investing activities	(9,573)	(3,468)
Financing activities
Proceeds from the issuance of common stock pursuant to employee equity plans	3,411	4,103
Tax payments related to net share settlements on restricted stock units	(10,860)	(3,307)
Borrowings from warehouse credit facilities	216,382	131,310
Repayments to warehouse credit facilities	(214,747)	(110,025)
Borrowings from secured revolving credit facility	71,177	11,854
Repayments to secured revolving credit facility	(46,275)	(7,398)
Proceeds from issuance of convertible senior notes, net of issuance costs	488,691	0
Purchases of capped calls related to convertible senior notes	(54,480)	0
Payments for repurchases and conversions of convertible senior notes	(1,886)	0
Other payables—deposits held in escrow	6,521	3,684
Principal payments under finance lease obligations	(67)	(15)
Cash paid for secured revolving credit facility issuance costs	(305)	0
Net cash provided by financing activities	457,562	30,206
Effect of exchange rate changes on cash and cash equivalents	1	(25)
Net change in cash, cash equivalents, and restricted cash	397,225	(16,736)
Cash, cash equivalents, and restricted cash:
Beginning of period	945,820	247,448
End of period	1,343,045	230,712
Supplemental disclosure of cash flow information
Cash paid for interest	973	1,582
Non-cash transactions
Stock-based compensation capitalized in property and equipment	732	504
Property and equipment additions in accounts payable and accrued liabilities	2,348	451
Leasehold improvements paid directly by lessor	$ 1,334	$ 0