Investment Securities - By Contractual Maturity (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Amortized Cost
Due in One Year or Less	$ 19,817
Due after One Year through Five Years	595,337
Due after Five Years through Ten Years	1,276,393
Due after Ten Years	1,016,964
Amortized  Cost	2,908,511	$ 4,278,589
Fair Value
Due in One Year or Less	19,806
Due after One Year through Five Years	567,921
Due after Five Years through Ten Years	1,162,325
Due after Ten Years	929,018
Total	2,679,070	4,273,864
Amortized Cost
Due in One Year or Less	0
Due after One Year through Five Years	0
Due after Five Years through Ten Years	60,867
Due after Ten Years	1,329,924
Total	1,390,791	381,696
Fair Value
Due in One Year or Less	0
Due after One Year through Five Years	0
Due after Five Years through Ten Years	56,380
Due after Ten Years	1,100,121
Total	1,156,501	384,423
Amortized Cost
Due in One Year or Less	19,817
Due after One Year through Five Years	595,337
Due after Five Years through Ten Years	1,337,260
Due after Ten Years	2,346,888
Total	4,299,302
Fair Value
Due in One Year or Less	19,806
Due after One Year through Five Years	567,921
Due after Five Years through Ten Years	1,218,705
Due after Ten Years	2,029,139
Total	3,835,571
U.S. Treasury
Amortized Cost
Due in One Year or Less	19,817
Due after One Year through Five Years	0
Due after Five Years through Ten Years	14,933
Due after Ten Years	0
Amortized  Cost	34,750	57,708
Fair Value
Due in One Year or Less	19,806
Due after One Year through Five Years	0
Due after Five Years through Ten Years	13,554
Due after Ten Years	0
Total	33,360	57,866
Agency
Amortized Cost
Due in One Year or Less	0
Due after One Year through Five Years	318,130
Due after Five Years through Ten Years	97,045
Due after Ten Years	37,670
Amortized  Cost	452,845	440,183
Fair Value
Due in One Year or Less	0
Due after One Year through Five Years	297,704
Due after Five Years through Ten Years	84,078
Due after Ten Years	30,513
Total	412,295	432,135
Corporate debt
Amortized Cost
Due in One Year or Less	0
Due after One Year through Five Years	229,675
Due after Five Years through Ten Years	372,645
Due after Ten Years	0
Amortized  Cost	602,320	451,621
Fair Value
Due in One Year or Less	0
Due after One Year through Five Years	223,185
Due after Five Years through Ten Years	346,230
Due after Ten Years	0
Total	569,415	453,861
Municipal bonds
Amortized Cost
Amortized  Cost		1,061,985
Fair Value
Total		1,089,913
Amortized Cost
Due in One Year or Less	0
Due after One Year through Five Years	0
Due after Five Years through Ten Years	60,867
Due after Ten Years	1,087,544
Total	1,148,411	368,344
Fair Value
Due in One Year or Less	0
Due after One Year through Five Years	0
Due after Five Years through Ten Years	56,380
Due after Ten Years	880,828
Total	937,208	370,507
Collateralized mortgage obligations
Amortized Cost
Due in One Year or Less	0
Due after One Year through Five Years	47,532
Due after Five Years through Ten Years	221,867
Due after Ten Years	562,942
Amortized  Cost	832,341	680,686
Fair Value
Due in One Year or Less	0
Due after One Year through Five Years	47,032
Due after Five Years through Ten Years	205,674
Due after Ten Years	537,080
Total	789,786	676,643
Mortgage-backed securities
Amortized Cost
Due in One Year or Less	0
Due after One Year through Five Years	0
Due after Five Years through Ten Years	569,903
Due after Ten Years	416,352
Amortized  Cost	986,255	1,586,406
Fair Value
Due in One Year or Less	0
Due after One Year through Five Years	0
Due after Five Years through Ten Years	512,789
Due after Ten Years	361,425
Total	874,214	1,563,446
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	240,918
Total	240,918	11,843
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	217,831
Total	217,831	$ 12,407
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	1,462
Total	1,462
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	1,462
Total	$ 1,462