Fair Value Measurement - Loans at Fair Value (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Financing Receivable, Past Due [Line Items]
Fair value	$ 597,981	$ 252,477
Loans (at fair value)
Financing Receivable, Past Due [Line Items]
Outstanding principal balance	636,132	277,228
Net fair value and accrued interest adjustments	(38,151)	(24,751)
Fair value	597,981	252,477
Loans (at fair value) | Auto Loans
Financing Receivable, Past Due [Line Items]
Fair value	230,800	50,100
Loans > 90 Days Past Due | Loans (at fair value)
Financing Receivable, Past Due [Line Items]
Outstanding principal balance	3,256	1,979
Net fair value and accrued interest adjustments	(2,970)	(1,692)
Fair value	$ 286	$ 287