Fair Value Measurements - Activity for Level 3 Assets Measured at Fair Value on a Recurring Basis (Details) - USD ($)	3 Months Ended			9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Level 3 CMO [Roll Forward]
Unrealized net holding gains (losses) on securities available-for-sale arising during the period	$ (63,956,000)	$ 54,076,000	$ 19,745,000	$ (101,403,000)	$ 119,708,000
Discounted Cash Flow
Level 3 CMO [Roll Forward]
Financing Receivable, before Allowance for Credit Loss, Average Yield				6.21%
Level 3
Level 3 CMO [Roll Forward]
Equity warrants, Balance, beginning of period				$ 4,520,000
Total included in earnings, Equity Warrants				25,351,000
Total included in other comprehensive income				0
Stock and Warrants Issued During Period, Value, Preferred Stock and Warrants				267,000
Sales, Equity Warrants				(25,809,000)
Net settlements, Equity Warrants				0
Fair Value, Equity, Transfers to Level 1, Amount				(582,000)
Fair Value, Measurements, Recurring
Level 3 CMO [Roll Forward]
Equity warrants, Balance, beginning of period				4,520,000
Equity warrants, Balance, end of period	3,747,000			3,747,000
Fair Value, Measurements, Recurring | Level 3
Level 3 CMO [Roll Forward]
Equity warrants, Balance, beginning of period				4,520,000
Equity warrants, Balance, end of period	3,747,000			3,747,000
Private Label CMOs | Fair Value, Measurements, Recurring | Level 3
Level 3 CMO [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value				4,647,000
Total included in earnings				263,000
Total included in other comprehensive income				(270,000)
Stock and Warrants Issued During Period, Value, Preferred Stock and Warrants				0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales				0
Net settlements				(819,000)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	3,821,000			3,821,000
Unrealized net holding gains (losses) on securities available-for-sale arising during the period				823,000
Fair Value, Equity, Transfers to Level 1, Amount				0
Asset-backed | Fair Value, Measurements, Recurring | Level 3
Level 3 CMO [Roll Forward]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value				25,725,000
Total included in earnings				(64,000)
Total included in other comprehensive income				(20,000)
Stock and Warrants Issued During Period, Value, Preferred Stock and Warrants				0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales				0
Net settlements				(7,312,000)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	$ 18,329,000			18,329,000
Unrealized net holding gains (losses) on securities available-for-sale arising during the period				136,000
Fair Value, Equity, Transfers to Level 1, Amount				0
Warrant
Level 3 CMO [Roll Forward]
Fair value transfers of assets measured on a recurring basis				$ 582,000