Securities Available for Sale - Additional information (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021		Jun. 30, 2020
Schedule of Securities Available-for-sale [Line Items]
Proceeds from sales of securities available for sale	$ 0	$ 0	$ 106,192,000	[1]	$ 2,396,000	[1]
Realized gains (losses) on sales of securities available for sale and other investments	148,000	(2,000)	(96,000)		(1,000)
Asset-backed securities related to Structured Program transactions
Schedule of Securities Available-for-sale [Line Items]
Credit loss (recovery) expense	$ (300,000)	(3,500,000)	$ (2,800,000)		7,500,000
Other asset-backed securities
Schedule of Securities Available-for-sale [Line Items]
Realized gains (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		$ 400,000			$ 1,000,000,000.0

[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.