CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
CASH FLOWS FROM OPERATING ACTIVITIES:
NET LOSS	$ (662)	$ (253)	$ (339)
Adjustments to reconcile net loss to cash, cash equivalents, and restricted cash (used in) provided by operating activities:
Depreciation and amortization	47	39	27
Amortization of right of use asset	8	24	12
Stock-based compensation	536	38	13
Warrant fair value adjustment	(12)	(31)	(6)
Gain on settlement of lease liabilities	(5)	0	0
Inventory valuation adjustment	56	8	32
Changes in fair value of derivative instruments	0	23	1
Changes in fair value of equity securities	(35)	0	0
Payment-in-kind interest	0	4	2
Net fair value adjustments and gain (loss) on sale of mortgage loans held for sale	(4)	(3)	0
Origination of mortgage loans held for sale	(196)	(128)	(23)
Proceeds from sale and principal collections of mortgage loans held for sale	197	126	22
Changes in operating assets and liabilities:
Escrow receivable	(83)	12	(3)
Real estate inventories	(5,656)	834	17
Other assets	(52)	3	(8)
Accounts payable and other accrued liabilities	76	(4)	(5)
Interest payable	4	(3)	0
Lease liabilities	(13)	(7)	(14)
Net cash (used in) provided by operating activities	(5,794)	682	(272)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchase of property and equipment	(33)	(17)	(28)
Purchase of intangible assets	(1)	0	0
Purchase of marketable securities	(486)	(175)	(79)
Proceeds from sales, maturities, redemptions and paydowns of marketable securities	92	170	45
Purchase of non-marketable equity securities	(15)	0	0
Acquisitions, net of cash acquired	(33)	0	(33)
Net cash used in investing activities	(476)	(22)	(95)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of convertible senior notes, net of issuance costs	953	0	178
Purchase of capped calls related to convertible senior notes	(119)	0	0
Proceeds from exercise of stock options	15	8	3
Proceeds from warrant exercise	22	0	0
Proceeds from Business Combination and PIPE offering	0	1,014	0
Proceeds from February 2021 Offering	886	0	0
Capital distributions of non-controlling interest	0	0	(3)
Proceeds from non-recourse asset-backed debt	11,499	1,309	3,641
Principal payments on non-recourse asset-backed debt	(5,838)	(2,130)	(3,475)
Proceeds from other secured borrowings	192	125	23
Principal payment on other secured borrowings	(192)	(121)	(21)
Payment of loan origination fees and debt issuance costs	(47)	(3)	(15)
Repurchase of common stock at fair value	0	0	(3)
Net cash provided by financing activities	7,342	161	646
NET INCREASE (DECREASE) IN CASH, CASH EQUIVALENTS, AND RESTRICTED CASH	1,072	821	279
CASH, CASH EQUIVALENTS, AND RESTRICTED CASH – Beginning of period	1,506	685	406
CASH, CASH EQUIVALENTS, AND RESTRICTED CASH – End of period	2,578	1,506	685
SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION – Cash paid during the period for interest	122	57	86
DISCLOSURES OF NONCASH FINANCING ACTIVITIES:
Conversion of preferred stock to common stock	0	1,386	0
Issuance of issuer stock rights in extinguishment of the 2019 Convertible Notes	0	213	0
Noncash financing, issuance of common stock for acquisition	0	0	7
Recognition of warrant liability	0	81	0
Issuance of common stock in extinguishment of warrant liabilities	(35)	0	0
RECONCILIATION TO CONDENSED CONSOLIDATED BALANCE SHEETS:
Cash and cash equivalents	1,731	1,413	405
Restricted cash	847	93	280
Cash, cash equivalents, and restricted cash	2,578	1,506	685
Series D Convertible Preferred Stock
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from Issuance of Convertible Preferred Stock	0	0	35
Series E Convertible Preferred Stock
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from Issuance of Convertible Preferred Stock	0	2	0
Series E-2 Convertible Preferred Stock
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from Issuance of Convertible Preferred Stock	0	0	283
Common Stock
CASH FLOWS FROM FINANCING ACTIVITIES:
Issuance cost of common stock	$ (29)	$ (43)	$ 0