Investment Securities - Amortized Cost and Fair Value of Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Available for sale debt securities
Amortized Cost	$ 2,466,109	$ 2,558,675
Unrealized Gains	525	43
Unrealized Losses	(307,296)	(303,382)
Total available-for-sale securities, Fair value,	2,159,338	2,255,336
Held to maturity securities
Amortized Cost	3,988,011	4,041,449
Unrealized Gains	167	195
Unrealized Losses	(517,468)	(466,788)
Total held to maturity, Fair value,	3,470,710	3,574,856
Available-for-sale investment securities
Accrued interest receivable related to available-for-sale investment securities	7,000	7,200
Accrued interest receivable related to held to maturity investment securities	7,300	7,000
Collateralized Loan Obligations
Available for sale debt securities
Amortized Cost	239,872	249,871
Unrealized Gains	383	43
Unrealized Losses	(579)	(2,060)
Total available-for-sale securities, Fair value,	239,676	247,854
U.S. Treasury and government agency debt securities
Available for sale debt securities
Amortized Cost	13,254	33,169
Unrealized Losses	(433)	(666)
Total available-for-sale securities, Fair value,	12,821	32,503
Government-sponsored enterprises debt securities
Available for sale debt securities
Amortized Cost	20,000	20,000
Unrealized Losses	(371)	(408)
Total available-for-sale securities, Fair value,	19,629	19,592
Government agency debt securities
Held to maturity securities
Amortized Cost	51,904	52,051
Unrealized Losses	(5,300)	(4,497)
Total held to maturity, Fair value,	46,604	47,554
Residential - Government agency
Available for sale debt securities
Amortized Cost	10,959	11,303
Unrealized Losses	(1,350)	(1,121)
Total available-for-sale securities, Fair value,	9,609	10,182
Held to maturity securities
Amortized Cost	42,961	43,885
Unrealized Losses	(6,209)	(5,189)
Total held to maturity, Fair value,	36,752	38,696
Residential - Government-sponsored enterprises
Available for sale debt securities
Amortized Cost	868,033	895,421
Unrealized Losses	(114,648)	(112,124)
Total available-for-sale securities, Fair value,	753,385	783,297
Held to maturity securities
Amortized Cost	97,914	99,379
Unrealized Losses	(13,466)	(11,013)
Total held to maturity, Fair value,	84,448	88,366
Commercial - Government agency
Available for sale debt securities
Amortized Cost	264,691	268,944
Unrealized Losses	(51,297)	(50,270)
Total available-for-sale securities, Fair value,	213,394	218,674
Held to maturity securities
Amortized Cost	30,853	30,795
Unrealized Losses	(7,651)	(7,017)
Total held to maturity, Fair value,	23,202	23,778
Commercial - Government-sponsored enterprises
Available for sale debt securities
Amortized Cost	90,441	93,459
Unrealized Losses	(6,951)	(7,028)
Total available-for-sale securities, Fair value,	83,490	86,431
Held to maturity securities
Amortized Cost	1,127,321	1,129,738
Unrealized Gains	167	195
Unrealized Losses	(144,378)	(130,757)
Total held to maturity, Fair value,	983,110	999,176
Commercial - Non -agency
Available for sale debt securities
Amortized Cost	21,968	21,964
Unrealized Gains	142
Unrealized Losses		(281)
Total available-for-sale securities, Fair value,	22,110	21,683
Government agency
Available for sale debt securities
Amortized Cost	523,160	538,718
Unrealized Losses	(70,997)	(67,568)
Total available-for-sale securities, Fair value,	452,163	471,150
Held to maturity securities
Amortized Cost	972,199	989,130
Unrealized Losses	(125,164)	(109,471)
Total held to maturity, Fair value,	847,035	879,659
Government-sponsored enterprises
Available for sale debt securities
Amortized Cost	413,731	425,826
Unrealized Losses	(60,670)	(61,856)
Total available-for-sale securities, Fair value,	353,061	363,970
Held to maturity securities
Amortized Cost	1,610,563	1,642,274
Unrealized Losses	(209,655)	(193,897)
Total held to maturity, Fair value,	1,400,908	1,448,377
Debt securities issued by states and political subdivisions
Held to maturity securities
Amortized Cost	54,296	54,197
Unrealized Losses	(5,645)	(4,947)
Total held to maturity, Fair value,	$ 48,651	$ 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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