Borrowings - Assets Pledged as Collateral (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Schedule of Borrowings [Line Items]
Outstanding borrowings	$ 709,787	$ 62,681
Aggregate fair value of loans purchased and held	252,477	78,460
Restricted cash	204,633	60,514
Variable Interest Entity, Primary Beneficiary
Schedule of Borrowings [Line Items]
Restricted cash	79,561	12,371
ULT Warehouse Credit Facility | Revolving credit facility | Variable Interest Entity, Primary Beneficiary
Schedule of Borrowings [Line Items]
Outstanding borrowings	48,030	34,994
Aggregate outstanding principal of loans pledged as collateral	76,865	59,709
Aggregate fair value of loans purchased and held	142,687	60,231
Restricted cash	$ 76,256	$ 11,270