Subordinated Debentures - Narrative (Details)		6 Months Ended
	Apr. 15, 2021 USD ($)	Jun. 30, 2021 USD ($) note	Jun. 30, 2020 USD ($)	Dec. 31, 2020 USD ($) note
Debt Instrument [Line Items]
Current Principal Balance		$ 480,403,000
Loss on early debt extinguishment		1,150,000	$ 0
Subordinated debentures		$ 476,622,000		$ 501,511,000
Subordinated notes
Debt Instrument [Line Items]
Number of notes/securities | note		4		5
Current Principal Balance	$ 25,000,000	$ 470,000,000
Fixed interest rate (as a percent)	7.125%
Redemption price (as a percent)	103.00%
Redemption amount	$ 25,800,000
Loss on early debt extinguishment	(647,000)
Purchase accounting adjustments	$ 103,000
Subordinated debentures		$ 468,449,000		$ 493,410,000
Weighted interest rate		5.29%		5.38%
Reduction in Tier 2 capital		$ 20,000,000
Subordinated debt
Debt Instrument [Line Items]
Number of notes/securities | note		2		2
Current Principal Balance		$ 10,403,000
Subordinated debentures		$ 8,173,000		$ 8,101,000