Investment Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Amortized Cost Basis	$ 4,996,970	$ 3,688,091
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	241,999	112,651
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(3,378)	(3,555)
Securities available-for-sale, at fair value	5,235,591	3,797,187
Municipal Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Amortized Cost Basis	1,438,004	691,647
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	93,631	43,851
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(18)	(339)
Securities available-for-sale, at fair value	1,531,617	735,159
Government agency and government-sponsored enterprise pass through securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Amortized Cost Basis	1,207,676	1,083,182
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	74,238	25,579
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(37)	(537)
Securities available-for-sale, at fair value	1,281,877	1,108,224
Government agency and government-sponsored enterprise collateralized mortgage obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Amortized Cost Basis	1,172,166	1,112,573
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	47,994	24,403
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(280)	(579)
Securities available-for-sale, at fair value	1,219,880	1,136,397
Residential Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Amortized Cost Basis	329,488	294,606
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	12,483	10,593
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(897)	(1)
Securities available-for-sale, at fair value	341,074	305,198
Corporate Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Amortized Cost Basis	308,803	17,000
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	3,490	3,748
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(404)	0
Securities available-for-sale, at fair value	311,889	20,748
Asset-backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Amortized Cost Basis	248,739	216,133
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	1,534	320
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(770)	(1,670)
Securities available-for-sale, at fair value	249,503	214,783
Collateralized Loan Obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Amortized Cost Basis	136,777	124,134
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	23	25
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(924)	(403)
Securities available-for-sale, at fair value	135,876	123,756
Private Label Collateralized Mortgage Obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Amortized Cost Basis	110,891	96,066
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	6,076	3,430
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(21)	(13)
Securities available-for-sale, at fair value	116,946	99,483
SBA asset-backed securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Amortized Cost Basis	39,437	47,765
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	2,217	506
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	(27)	(13)
Securities available-for-sale, at fair value	41,627	48,258
US Treasury Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities, Amortized Cost Basis	4,989	4,985
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	313	196
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	0	0
Securities available-for-sale, at fair value	$ 5,302	$ 5,181