Investment Securities - By Contractual Maturity (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Amortized Cost
Due in One Year or Less	$ 549,097
Due after One Year through Five Years	497,716
Due after Five Years through Ten Years	257,813
Due after Ten Years	45,299
Amortized  Cost	1,349,925	$ 1,176,040
Fair Value
Due in One Year or Less	548,723
Due after One Year through Five Years	496,072
Due after Five Years through Ten Years	230,376
Due after Ten Years	44,879
Total	1,320,050	1,140,071
Amortized Cost
Due in One Year or Less	0
Due after One Year through Five Years	34,380
Due after Five Years through Ten Years	50,879
Due after Ten Years	1,625,011
Total	1,710,270	1,729,667
Fair Value
Due in One Year or Less	0
Due after One Year through Five Years	32,006
Due after Five Years through Ten Years	44,645
Due after Ten Years	1,350,673
Total	1,427,324	1,485,506
Amortized Cost
Due in One Year or Less	549,097
Due after One Year through Five Years	532,096
Due after Five Years through Ten Years	308,692
Due after Ten Years	1,670,310
Total	3,060,195
Fair Value
Due in One Year or Less	548,723
Due after One Year through Five Years	528,078
Due after Five Years through Ten Years	275,021
Due after Ten Years	1,395,552
Total	2,747,374
U.S. Treasury
Amortized Cost
Due in One Year or Less	516,044
Due after One Year through Five Years	247,308
Due after Five Years through Ten Years	0
Due after Ten Years	0
Amortized  Cost	763,352	538,899
Fair Value
Due in One Year or Less	515,683
Due after One Year through Five Years	247,428
Due after Five Years through Ten Years	0
Due after Ten Years	0
Total	763,111	539,256
Agency
Amortized Cost
Due in One Year or Less	0
Due after One Year through Five Years	909
Due after Five Years through Ten Years	0
Due after Ten Years	674
Amortized  Cost	1,583	1,941
Fair Value
Due in One Year or Less	0
Due after One Year through Five Years	880
Due after Five Years through Ten Years	0
Due after Ten Years	646
Total	1,526	1,868
Corporate
Amortized Cost
Due in One Year or Less	33,004
Due after One Year through Five Years	203,424
Due after Five Years through Ten Years	204,937
Due after Ten Years	0
Amortized  Cost	441,365	481,499
Fair Value
Due in One Year or Less	32,991
Due after One Year through Five Years	201,827
Due after Five Years through Ten Years	177,844
Due after Ten Years	0
Total	412,662	446,343
Collateralized mortgage obligations
Amortized Cost
Due in One Year or Less	49
Due after One Year through Five Years	46,075
Due after Five Years through Ten Years	52,876
Due after Ten Years	44,625
Amortized  Cost	143,625	153,701
Fair Value
Due in One Year or Less	49
Due after One Year through Five Years	45,937
Due after Five Years through Ten Years	52,532
Due after Ten Years	44,233
Total	142,751	152,604
Amortized Cost
Due in One Year or Less	0
Due after One Year through Five Years	69
Due after Five Years through Ten Years	0
Due after Ten Years	323,463
Total	323,532	334,997
Fair Value
Due in One Year or Less	0
Due after One Year through Five Years	69
Due after Five Years through Ten Years	0
Due after Ten Years	312,685
Total	312,754	326,992
Municipal bonds
Amortized Cost
Due in One Year or Less	0
Due after One Year through Five Years	32,388
Due after Five Years through Ten Years	47,410
Due after Ten Years	1,065,765
Total	1,145,563	1,146,244
Fair Value
Due in One Year or Less	0
Due after One Year through Five Years	29,966
Due after Five Years through Ten Years	41,150
Due after Ten Years	838,525
Total	909,641	940,576
Mortgage-backed securities
Amortized Cost
Due in One Year or Less	0
Due after One Year through Five Years	1,923
Due after Five Years through Ten Years	3,469
Due after Ten Years	219,561
Total	224,953	232,157
Fair Value
Due in One Year or Less	0
Due after One Year through Five Years	1,971
Due after Five Years through Ten Years	3,495
Due after Ten Years	183,241
Total	188,707	$ 201,669
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	16,222
Total	16,222
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	16,222
Total	$ 16,222