Business Segment and Geographic Information - Schedule of Financial Results (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($) segment	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Segment Reporting Information [Line Items]
Net interest income (expense)	$ 1,261,740	$ 584,096	$ 252,244
Noninterest income (expense)	861,049	989,439	732,628
Total net revenue	$ 2,122,789	1,573,535	984,872
Number of reportable segments | segment	3
Reportable Segments
Segment Reporting Information [Line Items]
Net interest income (expense)	$ 1,297,134	624,054	261,838
Noninterest income (expense)	862,342	998,746	729,449
Total net revenue	2,159,476	1,622,800	991,287
Servicing rights – change in valuation inputs or assumptions	(34,700)	(39,651)	2,651
Residual interests classified as debt – change in valuation inputs or assumptions	425	6,608	22,802
Directly attributable expenses	(1,207,404)	(1,048,667)	(687,604)
Contribution profit (loss)	917,797	541,090	329,136
Intercompany expenses	22,199	7,604	1,863
Reportable Segments | Lending
Segment Reporting Information [Line Items]
Net interest income (expense)	960,773	531,480	258,102
Noninterest income (expense)	409,848	608,511	480,221
Total net revenue	1,370,621	1,139,991	738,323
Servicing rights – change in valuation inputs or assumptions	(34,700)	(39,651)	2,651
Residual interests classified as debt – change in valuation inputs or assumptions	425	6,608	22,802
Directly attributable expenses	(513,073)	(442,945)	(364,169)
Contribution profit (loss)	823,273	664,003	399,607
Reportable Segments | Technology Platform
Segment Reporting Information [Line Items]
Net interest income (expense)	1,514	0	(29)
Noninterest income (expense)	350,826	315,133	194,915
Total net revenue	352,340	315,133	194,886
Servicing rights – change in valuation inputs or assumptions	0	0	0
Residual interests classified as debt – change in valuation inputs or assumptions	0	0	0
Directly attributable expenses	(257,554)	(238,620)	(130,439)
Contribution profit (loss)	94,786	76,513	64,447
Reportable Segments | Financial Services
Segment Reporting Information [Line Items]
Net interest income (expense)	334,847	92,574	3,765
Noninterest income (expense)	101,668	75,102	54,313
Total net revenue	436,515	167,676	58,078
Servicing rights – change in valuation inputs or assumptions	0	0	0
Residual interests classified as debt – change in valuation inputs or assumptions	0	0	0
Directly attributable expenses	(436,777)	(367,102)	(192,996)
Contribution profit (loss)	(262)	(199,426)	(134,918)
Other
Segment Reporting Information [Line Items]
Net interest income (expense)	(35,394)	(39,958)	(9,594)
Noninterest income (expense)	(1,293)	(9,307)	3,179
Total net revenue	$ (36,687)	$ (49,265)	$ (6,415)