Investment Securities - Amortized Cost and Fair Value of Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Available for sale debt securities
Amortized Cost	$ 2,379,004	$ 2,558,675
Unrealized Gains	628	43
Unrealized Losses	(311,676)	(303,382)
Total available-for-sale securities, Fair value,	2,067,956	2,255,336
Held to maturity securities
Amortized Cost	3,917,175	4,041,449
Unrealized Gains	180	195
Unrealized Losses	(516,349)	(466,788)
Total held to maturity, Fair value,	3,401,006	3,574,856
Available-for-sale investment securities
Accrued interest receivable related to available-for-sale investment securities	6,400	7,200
Accrued interest receivable related to held to maturity investment securities	6,700	7,000
Collateralized Loan Obligations
Available for sale debt securities
Amortized Cost	217,400	249,871
Unrealized Gains	628	43
Unrealized Losses		(2,060)
Total available-for-sale securities, Fair value,	218,028	247,854
U.S. Treasury and government agency debt securities
Available for sale debt securities
Amortized Cost	13,287	33,169
Unrealized Losses	(318)	(666)
Total available-for-sale securities, Fair value,	12,969	32,503
Government-sponsored enterprises debt securities
Available for sale debt securities
Amortized Cost	20,000	20,000
Unrealized Losses	(332)	(408)
Total available-for-sale securities, Fair value,	19,668	19,592
Government agency debt securities
Held to maturity securities
Amortized Cost	50,589	52,051
Unrealized Losses	(5,284)	(4,497)
Total held to maturity, Fair value,	45,305	47,554
Residential - Government agency
Available for sale debt securities
Amortized Cost	10,765	11,303
Unrealized Losses	(1,430)	(1,121)
Total available-for-sale securities, Fair value,	9,335	10,182
Held to maturity securities
Amortized Cost	42,233	43,885
Unrealized Losses	(6,530)	(5,189)
Total held to maturity, Fair value,	35,703	38,696
Residential - Government-sponsored enterprises
Available for sale debt securities
Amortized Cost	838,352	895,421
Unrealized Losses	(117,207)	(112,124)
Total available-for-sale securities, Fair value,	721,145	783,297
Held to maturity securities
Amortized Cost	96,074	99,379
Unrealized Losses	(13,792)	(11,013)
Total held to maturity, Fair value,	82,282	88,366
Commercial - Government agency
Available for sale debt securities
Amortized Cost	262,848	268,944
Unrealized Losses	(54,620)	(50,270)
Total available-for-sale securities, Fair value,	208,228	218,674
Held to maturity securities
Amortized Cost	30,907	30,795
Unrealized Losses	(8,184)	(7,017)
Total held to maturity, Fair value,	22,723	23,778
Commercial - Government-sponsored enterprises
Available for sale debt securities
Amortized Cost	89,027	93,459
Unrealized Losses	(6,535)	(7,028)
Total available-for-sale securities, Fair value,	82,492	86,431
Held to maturity securities
Amortized Cost	1,120,320	1,129,738
Unrealized Gains	180	195
Unrealized Losses	(138,949)	(130,757)
Total held to maturity, Fair value,	981,551	999,176
Commercial - Non-agency
Available for sale debt securities
Amortized Cost	22,000	21,964
Unrealized Losses		(281)
Total available-for-sale securities, Fair value,	22,000	21,683
Government agency
Available for sale debt securities
Amortized Cost	505,180	538,718
Unrealized Losses	(70,324)	(67,568)
Total available-for-sale securities, Fair value,	434,856	471,150
Held to maturity securities
Amortized Cost	949,738	989,130
Unrealized Losses	(123,994)	(109,471)
Total held to maturity, Fair value,	825,744	879,659
Government-sponsored enterprises
Available for sale debt securities
Amortized Cost	400,145	425,826
Unrealized Losses	(60,910)	(61,856)
Total available-for-sale securities, Fair value,	339,235	363,970
Held to maturity securities
Amortized Cost	1,572,924	1,642,274
Unrealized Losses	(213,245)	(193,897)
Total held to maturity, Fair value,	1,359,679	1,448,377
Debt securities issued by states and political subdivisions
Held to maturity securities
Amortized Cost	54,390	54,197
Unrealized Losses	(6,371)	(4,947)
Total held to maturity, Fair value,	$ 48,019	$ 49,250

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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