Borrowings - Assets Pledged as Collateral (Details) - USD ($)	Mar. 31, 2022	Dec. 31, 2021
Schedule of Borrowings [Line Items]
Outstanding borrowings	$ 782,801,000	$ 709,787,000
Restricted cash	254,866,000	204,633,000
Variable Interest Entity, Primary Beneficiary
Schedule of Borrowings [Line Items]
Restricted cash	75,527,000	79,561,000
ULT Warehouse Credit Facility | Revolving Credit Facility | Variable Interest Entity, Primary Beneficiary
Schedule of Borrowings [Line Items]
Outstanding borrowings	90,113,000	48,030,000
Aggregate outstanding principal of loans pledged as collateral	123,362,000	76,865,000
Aggregate fair value of loans purchased and held	262,601,000	142,687,000
Restricted cash	34,996,000	76,256,000
UAWT Warehouse Credit Facility | Revolving Credit Facility | Variable Interest Entity, Primary Beneficiary
Schedule of Borrowings [Line Items]
Outstanding borrowings	31,438,000	$ 0
Aggregate outstanding principal of loans pledged as collateral	38,533,000
Aggregate fair value of loans purchased and held	57,549,000
Restricted cash	$ 578,000