Investment Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Amortized Cost Basis	$ 3,688,091	$ 4,017,909
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	112,651	31,812
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(3,555)	(40,290)
Securities available-for-sale, at fair value	3,797,187	4,009,431
Government agency and government-sponsored enterprise collateralized mortgage obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Amortized Cost Basis	1,112,573	634,774
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	24,403	3,448
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(579)	(5,372)
Securities available-for-sale, at fair value	1,136,397	632,850
Commercial Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Amortized Cost Basis	1,083,182	1,133,846
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	25,579	383
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(537)	(21,525)
Securities available-for-sale, at fair value	1,108,224	1,112,704
Municipal Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Amortized Cost Basis	691,647	1,298,514
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	43,851	21,000
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(339)	(7,320)
Securities available-for-sale, at fair value	735,159	1,312,194
Government agency and government-sponsored enterprise pass through securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Amortized Cost Basis	294,606	281,486
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	10,593	1,902
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(1)	(2,300)
Securities available-for-sale, at fair value	305,198	281,088
Asset-backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Amortized Cost Basis	216,133	81,762
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	320	104
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(1,670)	(481)
Securities available-for-sale, at fair value	214,783	81,385
Collateralized Loan Obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Amortized Cost Basis	124,134
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	25
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(403)
Securities available-for-sale, at fair value	123,756
Private Label Collateralized Mortgage Obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Amortized Cost Basis	96,066	101,313
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	3,430	1,985
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(13)	(2,093)
Securities available-for-sale, at fair value	99,483	101,205
SBA asset-backed securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Amortized Cost Basis	47,765	68,158
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	506	0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(13)	(1,111)
Securities available-for-sale, at fair value	48,258	67,047
Corporate Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Amortized Cost Basis	17,000	17,000
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	3,748	553
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	0	0
Securities available-for-sale, at fair value	20,748	17,553
US Treasury Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Amortized Cost Basis	4,985	401,056
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	196	2,437
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	0	(88)
Securities available-for-sale, at fair value	$ 5,181	$ 403,405