Investment Securities - By Contractual Maturity (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Amortized Cost
Due in One Year or Less	$ 68,424
Due after One Year through Five Years	689,930
Due after Five Years through Ten Years	1,107,486
Due after Ten Years	500,033
Amortized  Cost	2,365,873	$ 2,904,745
Fair Value
Due in One Year or Less	67,757
Due after One Year through Five Years	657,732
Due after Five Years through Ten Years	961,462
Due after Ten Years	425,901
Total	2,112,852	2,601,013
Amortized Cost
Due in One Year or Less	0
Due after One Year through Five Years	10,740
Due after Five Years through Ten Years	53,233
Due after Ten Years	1,685,284
Total	1,749,257	1,388,146
Fair Value
Due in One Year or Less	0
Due after One Year through Five Years	10,375
Due after Five Years through Ten Years	47,646
Due after Ten Years	1,438,473
Total	1,496,494	1,097,096
Amortized Cost
Due in One Year or Less	68,424
Due after One Year through Five Years	700,670
Due after Five Years through Ten Years	1,160,719
Due after Ten Years	2,185,317
Total	4,115,130
Fair Value
Due in One Year or Less	67,757
Due after One Year through Five Years	668,107
Due after Five Years through Ten Years	1,009,108
Due after Ten Years	1,864,374
Total	3,609,346
U.S. Treasury
Amortized Cost
Due in One Year or Less	0
Due after One Year through Five Years	0
Due after Five Years through Ten Years	14,941
Due after Ten Years	0
Amortized  Cost	14,941	49,156
Fair Value
Due in One Year or Less	0
Due after One Year through Five Years	0
Due after Five Years through Ten Years	13,355
Due after Ten Years	0
Total	13,355	47,017
Agency
Amortized Cost
Due in One Year or Less	17,140
Due after One Year through Five Years	314,788
Due after Five Years through Ten Years	107,278
Due after Ten Years	25,285
Amortized  Cost	464,491	485,331
Fair Value
Due in One Year or Less	16,966
Due after One Year through Five Years	292,224
Due after Five Years through Ten Years	89,306
Due after Ten Years	19,235
Total	417,731	431,438
Corporate
Amortized Cost
Due in One Year or Less	0
Due after One Year through Five Years	288,259
Due after Five Years through Ten Years	273,121
Due after Ten Years	0
Amortized  Cost	561,380	586,652
Fair Value
Due in One Year or Less	0
Due after One Year through Five Years	280,121
Due after Five Years through Ten Years	228,068
Due after Ten Years	0
Total	508,189	542,548
Collateralized mortgage obligations
Amortized Cost
Due in One Year or Less	31,382
Due after One Year through Five Years	71,997
Due after Five Years through Ten Years	199,472
Due after Ten Years	98,254
Amortized  Cost	401,105	829,928
Fair Value
Due in One Year or Less	31,174
Due after One Year through Five Years	70,731
Due after Five Years through Ten Years	178,056
Due after Ten Years	92,671
Total	372,632	764,229
Amortized Cost
Due in One Year or Less	0
Due after One Year through Five Years	151
Due after Five Years through Ten Years	0
Due after Ten Years	356,284
Total	356,435
Fair Value
Due in One Year or Less	0
Due after One Year through Five Years	151
Due after Five Years through Ten Years	0
Due after Ten Years	357,001
Total	357,152
Mortgage-backed securities
Amortized Cost
Due in One Year or Less	19,902
Due after One Year through Five Years	14,886
Due after Five Years through Ten Years	512,674
Due after Ten Years	376,494
Amortized  Cost	923,956	953,678
Fair Value
Due in One Year or Less	19,617
Due after One Year through Five Years	14,656
Due after Five Years through Ten Years	452,677
Due after Ten Years	313,995
Total	800,945	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	228,624
Total	228,624	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	198,003
Total	198,003	198,071
Municipal bonds
Amortized Cost
Due in One Year or Less	0
Due after One Year through Five Years	10,589
Due after Five Years through Ten Years	53,233
Due after Ten Years	1,084,000
Total	1,147,822	1,148,055
Fair Value
Due in One Year or Less	0
Due after One Year through Five Years	10,224
Due after Five Years through Ten Years	47,646
Due after Ten Years	867,093
Total	924,963	$ 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	16,376
Total	16,376
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	16,376
Total	$ 16,376