Investment Securities - Age of Unrealized Losses and Fair Value of Related Debt Securities Held to Maturity (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023
Fair Value
Less than Twelve Months	$ 328,108	$ 136,920
More than Twelve Months	2,492,592	2,751,924
Total	2,820,700	2,888,844
Unrealized Losses
Less than Twelve Months	(3,761)	(1,368)
More than Twelve Months	(502,282)	(443,384)
Total	(506,043)	(444,752)
U.S. Treasury securities
Fair Value
Less than Twelve Months	25,461	0
More than Twelve Months	0	25,978
Total	25,461	25,978
Unrealized Losses
Less than Twelve Months	(19)	0
More than Twelve Months	0	(254)
Total	(19)	(254)
U.S. government agency securities
Fair Value
Less than Twelve Months	22,621	43,664
More than Twelve Months	229,143	216,759
Total	251,764	260,423
Unrealized Losses
Less than Twelve Months	(75)	(151)
More than Twelve Months	(48,938)	(44,290)
Total	(49,013)	(44,441)
Obligations of states and state agencies
Fair Value
Less than Twelve Months	20,632	10,700
More than Twelve Months	42,058	48,149
Total	62,690	58,849
Unrealized Losses
Less than Twelve Months	(517)	(102)
More than Twelve Months	(4,818)	(4,053)
Total	(5,335)	(4,155)
Municipal bonds
Fair Value
Less than Twelve Months	36,766	11,958
More than Twelve Months	210,723	207,520
Total	247,489	219,478
Unrealized Losses
Less than Twelve Months	(440)	(121)
More than Twelve Months	(20,362)	(14,259)
Total	(20,802)	(14,380)
Total obligations of states and political subdivisions
Fair Value
Less than Twelve Months	57,398	22,658
More than Twelve Months	252,781	255,669
Total	310,179	278,327
Unrealized Losses
Less than Twelve Months	(957)	(223)
More than Twelve Months	(25,180)	(18,312)
Total	(26,137)	(18,535)
Residential mortgage-backed securities
Fair Value
Less than Twelve Months	216,651	57,085
More than Twelve Months	1,917,644	2,164,704
Total	2,134,295	2,221,789
Unrealized Losses
Less than Twelve Months	(2,687)	(505)
More than Twelve Months	(417,895)	(368,931)
Total	(420,582)	(369,436)
Trust preferred securities
Fair Value
Less than Twelve Months	0	938
More than Twelve Months	29,145	29,712
Total	29,145	30,650
Unrealized Losses
Less than Twelve Months	0	(63)
More than Twelve Months	(6,936)	(6,349)
Total	(6,936)	(6,412)
Corporate and other debt securities
Fair Value
Less than Twelve Months	5,977	12,575
More than Twelve Months	63,879	59,102
Total	69,856	71,677
Unrealized Losses
Less than Twelve Months	(23)	(426)
More than Twelve Months	(3,333)	(5,248)
Total	$ (3,356)	$ (5,674)

Amount of accumulated unrealized loss on investment in debt security measured at amortized cost (held-to-maturity).

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Amount of accumulated unrealized loss on investment in debt security measured at amortized cost (held-to-maturity), in continuous loss position for 12 months or longer.

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Fair value of investment in debt security measured at amortized cost (held-to-maturity), in unrealized loss position.

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