Investment Securities - Amortized Cost and Fair Value of Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Available for sale debt securities
Amortized Cost	$ 2,290,781	$ 2,558,675
Unrealized Gains	465	43
Unrealized Losses	(235,287)	(303,382)
Total available-for-sale securities, Fair value,	2,055,959	2,255,336
Held to maturity securities
Amortized Cost	3,853,697	4,041,449
Unrealized Gains	210	195
Unrealized Losses	(378,764)	(466,788)
Total held to maturity, Fair value,	3,475,143	3,574,856
Available-for-sale investment securities
Accrued interest receivable related to available-for-sale investment securities	6,200	7,200
Accrued interest receivable related to held to maturity investment securities	7,000
Collateralized loan obligations
Available for sale debt securities
Amortized Cost	208,550	249,871
Unrealized Gains	396	43
Unrealized Losses	(2)	(2,060)
Total available-for-sale securities, Fair value,	208,944	247,854
U.S. Treasury and government agency debt securities
Available for sale debt securities
Amortized Cost	13,320	33,169
Unrealized Losses	(123)	(666)
Total available-for-sale securities, Fair value,	13,197	32,503
Government-sponsored enterprises debt securities
Available for sale debt securities
Amortized Cost	20,000	20,000
Unrealized Losses	(153)	(408)
Total available-for-sale securities, Fair value,	19,847	19,592
Government agency debt securities
Held to maturity securities
Amortized Cost	50,424	52,051
Unrealized Losses	(3,421)	(4,497)
Total held to maturity, Fair value,	47,003	47,554
Residential - Government agency
Available for sale debt securities
Amortized Cost	10,356	11,303
Unrealized Losses	(989)	(1,121)
Total available-for-sale securities, Fair value,	9,367	10,182
Held to maturity securities
Amortized Cost	41,584	43,885
Unrealized Losses	(4,652)	(5,189)
Total held to maturity, Fair value,	36,932	38,696
Residential - Government-sponsored enterprises
Available for sale debt securities
Amortized Cost	807,631	895,421
Unrealized Losses	(84,040)	(112,124)
Total available-for-sale securities, Fair value,	723,591	783,297
Held to maturity securities
Amortized Cost	94,039	99,379
Unrealized Losses	(9,769)	(11,013)
Total held to maturity, Fair value,	84,270	88,366
Commercial - Government agency
Available for sale debt securities
Amortized Cost	260,845	268,944
Unrealized Losses	(44,835)	(50,270)
Total available-for-sale securities, Fair value,	216,010	218,674
Held to maturity securities
Amortized Cost	30,960	30,795
Unrealized Losses	(7,004)	(7,017)
Total held to maturity, Fair value,	23,956	23,778
Commercial - Government-sponsored enterprises
Available for sale debt securities
Amortized Cost	73,614	93,459
Unrealized Losses	(4,547)	(7,028)
Total available-for-sale securities, Fair value,	69,067	86,431
Held to maturity securities
Amortized Cost	1,118,670	1,129,738
Unrealized Gains	210	195
Unrealized Losses	(97,680)	(130,757)
Total held to maturity, Fair value,	1,021,200	999,176
Commercial - Non-agency
Available for sale debt securities
Amortized Cost	22,000	21,964
Unrealized Gains	69
Unrealized Losses		(281)
Total available-for-sale securities, Fair value,	22,069	21,683
Government agency
Available for sale debt securities
Amortized Cost	487,889	538,718
Unrealized Losses	(53,748)	(67,568)
Total available-for-sale securities, Fair value,	434,141	471,150
Held to maturity securities
Amortized Cost	928,546	989,130
Unrealized Losses	(94,856)	(109,471)
Total held to maturity, Fair value,	833,690	879,659
Government-sponsored enterprises
Available for sale debt securities
Amortized Cost	386,576	425,826
Unrealized Losses	(46,850)	(61,856)
Total available-for-sale securities, Fair value,	339,726	363,970
Held to maturity securities
Amortized Cost	1,534,983	1,642,274
Unrealized Losses	(157,632)	(193,897)
Total held to maturity, Fair value,	1,377,351	1,448,377
Debt securities issued by states and political subdivisions
Held to maturity securities
Amortized Cost	54,491	54,197
Unrealized Losses	(3,750)	(4,947)
Total held to maturity, Fair value,	$ 50,741	$ 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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