Securities Available for Sale - Additional information (Details) - USD ($)		3 Months Ended		9 Months Ended
		Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Schedule of Securities Available-for-sale [Line Items]
Proceeds from sales of securities available for sale	[1]			$ 106,192,000	$ 2,396,000
Realized losses on sales of securities available for sale and other investments		$ 0	$ 0	(96,000)	(1,000)
Asset-backed securities related to Structured Program transactions
Schedule of Securities Available-for-sale [Line Items]
Credit loss (recovery) expense		$ (500,000)	(3,700,000)	$ (3,300,000)	3,800,000
Other asset-backed securities
Schedule of Securities Available-for-sale [Line Items]
Realized losses on sales of securities available for sale and other investments			0		0
Other asset-backed securities | Depositor
Schedule of Securities Available-for-sale [Line Items]
Proceeds from sales of securities available for sale			$ 200,000,000		$ 1,300,000,000

[1] Prior period amounts have been reclassified to conform to the current period presentation. See “Notes to Condensed Consolidated Financial Statements – Note 1. Summary of Significant Accounting Policies” for additional information.