Investment Securities - By Contractual Maturity (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Amortized Cost
Due in One Year or Less	$ 69,892
Due after One Year through Five Years	755,138
Due after Five Years through Ten Years	1,178,255
Due after Ten Years	982,106
Amortized  Cost	2,985,391	$ 4,278,589
Fair Value
Due in One Year or Less	69,394
Due after One Year through Five Years	715,115
Due after Five Years through Ten Years	1,019,911
Due after Ten Years	856,659
Total	2,661,079	4,273,864
Amortized Cost
Due in One Year or Less	0
Due after One Year through Five Years	10,484
Due after Five Years through Ten Years	50,556
Due after Ten Years	1,324,553
Total	1,385,593	381,696
Fair Value
Due in One Year or Less	0
Due after One Year through Five Years	9,749
Due after Five Years through Ten Years	43,410
Due after Ten Years	1,002,028
Total	1,055,187	384,423
Amortized Cost
Due in One Year or Less	69,892
Due after One Year through Five Years	765,622
Due after Five Years through Ten Years	1,228,811
Due after Ten Years	2,306,659
Total	4,370,984
Fair Value
Due in One Year or Less	69,394
Due after One Year through Five Years	724,864
Due after Five Years through Ten Years	1,063,321
Due after Ten Years	1,858,687
Total	3,716,266
U.S. Treasury
Amortized Cost
Due in One Year or Less	9,648
Due after One Year through Five Years	24,342
Due after Five Years through Ten Years	14,936
Due after Ten Years	0
Amortized  Cost	48,926	57,708
Fair Value
Due in One Year or Less	9,639
Due after One Year through Five Years	24,226
Due after Five Years through Ten Years	12,909
Due after Ten Years	0
Total	46,774	57,866
Agency
Amortized Cost
Due in One Year or Less	25,583
Due after One Year through Five Years	326,627
Due after Five Years through Ten Years	96,469
Due after Ten Years	37,432
Amortized  Cost	486,111	440,183
Fair Value
Due in One Year or Less	25,329
Due after One Year through Five Years	298,271
Due after Five Years through Ten Years	79,143
Due after Ten Years	28,120
Total	430,863	432,135
Corporate debt
Amortized Cost
Due in One Year or Less	0
Due after One Year through Five Years	298,578
Due after Five Years through Ten Years	303,480
Due after Ten Years	0
Amortized  Cost	602,058	451,621
Fair Value
Due in One Year or Less	0
Due after One Year through Five Years	289,014
Due after Five Years through Ten Years	266,736
Due after Ten Years	0
Total	555,750	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	10,484
Due after Five Years through Ten Years	50,556
Due after Ten Years	1,087,194
Total	1,148,234	368,344
Fair Value
Due in One Year or Less	0
Due after One Year through Five Years	9,749
Due after Five Years through Ten Years	43,410
Due after Ten Years	800,545
Total	853,704	370,507
Collateralized mortgage obligations
Amortized Cost
Due in One Year or Less	34,661
Due after One Year through Five Years	70,542
Due after Five Years through Ten Years	213,821
Due after Ten Years	537,843
Amortized  Cost	856,867	680,686
Fair Value
Due in One Year or Less	34,426
Due after One Year through Five Years	68,834
Due after Five Years through Ten Years	192,325
Due after Ten Years	495,530
Total	791,115	676,643
Mortgage-backed securities
Amortized Cost
Due in One Year or Less	0
Due after One Year through Five Years	35,049
Due after Five Years through Ten Years	549,549
Due after Ten Years	406,831
Amortized  Cost	991,429	1,586,406
Fair Value
Due in One Year or Less	0
Due after One Year through Five Years	34,770
Due after Five Years through Ten Years	468,798
Due after Ten Years	333,009
Total	836,577	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	235,937
Total	235,937	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	200,061
Total	200,061	$ 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	1,422
Total	1,422
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	1,422
Total	$ 1,422