Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Operating Activities
Net loss	$ (82,611)	$ (32,562)
Adjustments to reconcile net loss to net cash (used in) provided by operating activities:
Depreciation and amortization	32,303	10,581
Stock-based compensation	39,438	25,764
Amortization of debt discount and issuance costs	3,583	5,254
Non-cash lease expense	8,510	6,821
Impairment costs	0	2,063
Net loss (gain) on IRLCs, forward sales commitments, and loans held for sale	342	(2,303)
Other	(3,847)	(306)
Change in assets and liabilities:
Accounts receivable, net	(29,487)	(21,862)
Inventory	(385,986)	49,597
Prepaid expenses and other assets	(9,532)	7,396
Accounts payable	616	851
Accrued liabilities, other payables, deferred tax liabilities, and payroll tax liabilities, noncurrent	23,011	28,157
Lease liabilities	(9,644)	(8,368)
Origination of loans held for sale	(745,703)	(479,153)
Proceeds from sale of loans originated as held for sale	744,886	459,605
Net cash (used in) provided by operating activities	(414,121)	51,535
Investing activities
Purchases of property and equipment	(20,575)	(10,391)
Purchases of investments	(129,277)	(135,118)
Sales of investments	98,687	6,583
Maturities of investments	96,303	82,772
Cash paid for acquisition	(608,000)	0
Net cash used in investing activities	(562,862)	(56,154)
Financing activities
Proceeds from the issuance of convertible preferred stock, net of issuance costs	0	39,801
Proceeds from the issuance of common stock, net of issuance costs	0	69,701
Proceeds from the issuance of common stock pursuant to employee equity plans	14,194	15,119
Tax payments related to net share settlements on restricted stock units	(21,088)	(10,987)
Borrowings from warehouse credit facilities	710,535	473,283
Repayments to warehouse credit facilities	(709,739)	(454,277)
Borrowings from secured revolving credit facility	431,717	57,378
Repayments to secured revolving credit facility	(256,039)	(46,899)
Proceeds from issuance of convertible senior notes, net of issuance costs	561,529	0
Purchases of capped calls related to convertible senior notes	(62,647)	0
Payments for repurchases and conversions of convertible senior notes	(2,159)	0
Other payables—deposits held in escrow	3,161	2,097
Principal payments under finance lease obligations	(567)	(59)
Cash paid for secured revolving credit facility issuance costs	(485)	(4)
Net cash provided by financing activities	668,412	145,153
Effect of exchange rate changes on cash, cash equivalents, and restricted cash	(3)	(16)
Net change in cash, cash equivalents, and restricted cash	(308,574)	140,518
Cash, cash equivalents, and restricted cash:
Beginning of period	945,820	247,448
End of period	637,246	387,966
Supplemental disclosure of cash flow information
Cash paid for interest	5,539	3,001
Non-cash transactions
Stock-based compensation capitalized in property and equipment	2,745	1,714
Property and equipment additions in accounts payable and accrued liabilities	0	973
Leasehold improvements paid directly by lessor	$ 1,334	$ 37