Fair Value Measurements - Sensitivity of Fair Value of Loans Invested in by the Company, Asset-backed Securities Related to Structured Program Transactions and Servicing Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Servicing assets	$ 77,680	$ 84,308
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Servicing assets	77,680	84,308
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Servicing assets	77,680	84,308	$ 67,726
Servicing rate increase by .1%	8,719	10,505
Fair Value, Measurements, Recurring | Level 3 | Servicing Assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Servicing assets	77,680	84,308
Expected credit loss on rates on underlying loans, 10% adverse change	(878)	(1,037)
Expected credit loss on rates on underlying loans, 20% adverse change	(1,756)	(2,074)
Expected prepayment rates, 10% adverse change	(1,550)	(1,994)
Expected prepayment rates, 20% adverse change	(3,100)	(3,989)
Sensitivity Analysis of Fair Value, Transferor's Interests in Transferred Financial Assets, Impact of Other than 10 or 20 Percent Adverse Change in Discount Rate, 100 Basis Point Increase	(675)	(726)
Sensitivity Analysis of Fair Value, Transferor's Interests in Transferred Financial Assets, Impact of Other than 10 or 20 Percent Adverse Change in Discount Rate, 200 Basis Point Increase	$ (1,349)	$ (1,451)
Expected remaining weighted-average life (in years)	1 year 2 months 12 days	1 year 2 months 12 days