Investment Securities - By Contractual Maturity (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Amortized Cost
Due in One Year or Less	$ 60,630
Due after One Year through Five Years	672,420
Due after Five Years through Ten Years	1,075,617
Due after Ten Years	477,869
Amortized  Cost	2,286,536	$ 2,904,745
Fair Value
Due in One Year or Less	60,093
Due after One Year through Five Years	640,356
Due after Five Years through Ten Years	911,873
Due after Ten Years	399,469
Total	2,011,791	2,601,013
Amortized Cost
Due in One Year or Less	0
Due after One Year through Five Years	10,773
Due after Five Years through Ten Years	53,352
Due after Ten Years	1,673,592
Total	1,737,717	1,388,146
Fair Value
Due in One Year or Less	0
Due after One Year through Five Years	10,311
Due after Five Years through Ten Years	47,279
Due after Ten Years	1,400,697
Total	1,458,287	1,097,096
Amortized Cost
Due in One Year or Less	60,630
Due after One Year through Five Years	683,193
Due after Five Years through Ten Years	1,128,969
Due after Ten Years	2,151,461
Total	4,024,253
Fair Value
Due in One Year or Less	60,093
Due after One Year through Five Years	650,667
Due after Five Years through Ten Years	959,152
Due after Ten Years	1,800,166
Total	3,470,078
U.S. Treasury
Amortized Cost
Due in One Year or Less	0
Due after One Year through Five Years	14,944
Due after Five Years through Ten Years	0
Due after Ten Years	0
Amortized  Cost	14,944	49,156
Fair Value
Due in One Year or Less	0
Due after One Year through Five Years	13,104
Due after Five Years through Ten Years	0
Due after Ten Years	0
Total	13,104	47,017
Agency
Amortized Cost
Due in One Year or Less	17,140
Due after One Year through Five Years	314,680
Due after Five Years through Ten Years	106,988
Due after Ten Years	25,150
Amortized  Cost	463,958	485,331
Fair Value
Due in One Year or Less	16,989
Due after One Year through Five Years	289,909
Due after Five Years through Ten Years	88,101
Due after Ten Years	18,856
Total	413,855	431,438
Corporate
Amortized Cost
Due in One Year or Less	0
Due after One Year through Five Years	288,165
Due after Five Years through Ten Years	272,963
Due after Ten Years	0
Amortized  Cost	561,128	586,652
Fair Value
Due in One Year or Less	0
Due after One Year through Five Years	283,555
Due after Five Years through Ten Years	214,564
Due after Ten Years	0
Total	498,119	542,548
Collateralized mortgage obligations
Amortized Cost
Due in One Year or Less	15,504
Due after One Year through Five Years	54,631
Due after Five Years through Ten Years	193,285
Due after Ten Years	94,346
Amortized  Cost	357,766	829,928
Fair Value
Due in One Year or Less	15,441
Due after One Year through Five Years	53,788
Due after Five Years through Ten Years	170,373
Due after Ten Years	87,655
Total	327,257	764,229
Amortized Cost
Due in One Year or Less	0
Due after One Year through Five Years	132
Due after Five Years through Ten Years	0
Due after Ten Years	349,196
Total	349,328
Fair Value
Due in One Year or Less	0
Due after One Year through Five Years	132
Due after Five Years through Ten Years	0
Due after Ten Years	341,881
Total	342,013
Mortgage-backed securities
Amortized Cost
Due in One Year or Less	27,986
Due after One Year through Five Years	0
Due after Five Years through Ten Years	502,381
Due after Ten Years	358,373
Amortized  Cost	888,740	953,678
Fair Value
Due in One Year or Less	27,663
Due after One Year through Five Years	0
Due after Five Years through Ten Years	438,835
Due after Ten Years	292,958
Total	759,456	815,781
Amortized Cost
Due in One Year or Less	0
Due after One Year through Five Years	0
Due after Five Years through Ten Years	0
Due after Ten Years	224,470
Total	224,470	231,692
Fair Value
Due in One Year or Less	0
Due after One Year through Five Years	0
Due after Five Years through Ten Years	0
Due after Ten Years	191,010
Total	191,010	198,071
Municipal bonds
Amortized Cost
Due in One Year or Less	0
Due after One Year through Five Years	10,641
Due after Five Years through Ten Years	53,352
Due after Ten Years	1,083,611
Total	1,147,604	1,148,055
Fair Value
Due in One Year or Less	0
Due after One Year through Five Years	10,179
Due after Five Years through Ten Years	47,279
Due after Ten Years	851,491
Total	908,949	$ 890,626
Other
Amortized Cost
Due in One Year or Less	0
Due after One Year through Five Years	0
Due after Five Years through Ten Years	0
Due after Ten Years	16,315
Total	16,315
Fair Value
Due in One Year or Less	0
Due after One Year through Five Years	0
Due after Five Years through Ten Years	0
Due after Ten Years	16,315
Total	$ 16,315