Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities
Net income		$ 135,443	$ 5,579	$ (5,020)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Change in fair value of financial instruments	[1]	(228)	29,049	34,716
Stock-based compensation		73,186	11,513	3,806
Loss (gain) on loan servicing arrangements and sale of noncontrolling interests, net		(6,916)	(1,530)	856
Depreciation and amortization		7,541	2,278	774
Incentive share expense		0	787	0
Non-cash interest expense		1,983	73	74
Gain on repurchased and retired convertible preferred stock warrants		0	0	(3,657)
Net changes in operating assets and liabilities:
Purchase of loans for immediate resale		(8,713,476)	(2,540,948)	(1,779,180)
Proceeds from immediate resale of loans		8,713,476	2,540,948	1,779,180
Purchase of loans held-for-sale		(219,128)	(116,127)	0
Principal payments received for loans held-for-sale		8,659	18,218	0
Net proceeds from sale of loans held-for-sale		112,569	47,604	0
Other assets		(62,042)	(13,186)	(11,957)
Operating lease liability and right-of-use asset		3,126	251	871
Accounts payable		(7,513)	7,033	3,613
Payable to investors		62,097	19,446	(14,875)
Accrued expenses and other liabilities		59,576	4,709	22,381
Net cash provided by operating activities		168,353	15,697	31,582
Cash flows from investing activities
Principal payments received for loans held by consolidated securitizations		0	24,018	158,921
Net proceeds from sale of loans held-for-investment		51,403	97,340	100,678
Principal payments received for loans held-for-investment		24,532	15,758	48,124
Principal payments received for notes receivable and repayments of residual certificates		11,458	14,665	8,760
Purchase of loans held-for-investment		(159,398)	(9,655)	(265,286)
Purchase of non-marketable equity security		(40,000)	0	0
Purchase of notes receivable and residual certificates		0	(4)	(485)
Purchase of property and equipment		(8,427)	(1,355)	(4,004)
Capitalized software costs		(6,688)	(4,250)	(1,275)
Acquisition, net of cash acquired		(16,757)	0	0
Net cash (used in) provided by investing activities		(143,877)	136,517	45,433
Cash flows from financing activities
Proceeds from initial public offering, net of underwriting discounts and offering costs		0	159,488	0
Proceeds from secondary offering, net of underwriting discounts, commissions, and offering costs		263,931	0	0
Proceeds from borrowings		718,422	92,057	153,491
Payment of debt issuance costs		(15,727)	0	0
Purchase of capped calls		(58,523)	0	0
Taxes paid related to net share settlement of equity awards		(236)	0	0
Payments made on securitization notes and certificates (b)	[2]	0	(26,126)	(176,742)
Repayments of borrowings		(71,316)	(148,113)	(109,939)
Repayments of notes payable		0	0	(22,637)
Distributions made to noncontrolling interests		0	(622)	(4,960)
Repurchase and retirement of convertible preferred stock warrants		0	0	(1,426)
Repurchase and retirement of convertible preferred stock		0	0	(661)
Proceeds from issuance of notes payable		0	0	39,863
Proceeds from issuance of convertible preferred stock, net of issuance costs		0	0	1,912
Proceeds from exercise of convertible preferred stock warrants		0	6	1,631
Proceeds from issuance of common stock under employee stock purchase plan		4,145	0	0
Proceeds from exercise of stock options		14,736	2,362	278
Net cash (used in) provided by financing activities		855,432	79,052	(119,190)
Net increase (decrease) in cash and restricted cash		879,908	231,266	(42,175)
Cash and restricted cash
Cash and restricted cash at beginning of year		311,333	80,067	122,242
Cash and restricted cash at end of year		1,191,241	311,333	80,067
Supplemental disclosures of cash flow information
Cash paid for interest		3,274	8,028	26,871
Cash paid for income taxes		2,300	0	0
Supplemental disclosures of non-cash investing and financing activities
Reclassification of common stock warrant liability related to cashless exercise		0	2,971	0
Reclassification of preferred stock warrant liability related to cash exercise		0	12,177	0
Reclassification of common stock warrant liability to equity upon termination of repurchase option		0	2,945	0
Issuance of common stock in connection with acquisition		80,256	0	0
Derecognition of loans held-for-investment in consolidated VIE		0	57,222	154,864
Derecognition of payable to securitization note holders and residual certificate holders		0	58,017	80,825
Derecognition of notes payable held in consolidated VIE		0	0	69,419
Securities retained under unconsolidated securitization transactions		0	0	31,160
Transfer of notes receivable and residual certificate on deconsolidation of VIE		0	0	3,699
Capitalized stock-based compensation expense		$ 3,141	$ 492	$ 0

[1] Includes $(7,400) and $(4,238) from related parties for the years ended December 31, 2019 and 2020, respectively.

[2] Includes $3,262 and $1,034 paid to related parties for the years ended December 31, 2019 and 2020, respectively.