Securities - Schedule of Amortized Cost and Fair Value of Investment Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Marketable Securities [Line Items]
Available for Sale, Amortized Cost	$ 318,253	$ 440,358
Available for Sale, Gross Unrealized Gains	1,888	2,890
Available for Sale, Gross Unrealized Losses	(4,841)	(4,660)
Available for Sale	315,300	438,588
Held to Maturity, Amortized Cost	11,985,838	12,365,308
Held to Maturity, Gross Unrealized Gains	1,152	3,995
Held to Maturity, Gross Unrealized Losses	(1,508,631)	(1,384,705)
Held to Maturity	10,478,359	10,984,598	$ 10,984,598
Corporate Debt Securities [Member]
Marketable Securities [Line Items]
Available for Sale, Amortized Cost	14,350	20,698
Available for Sale, Gross Unrealized Gains	1,830	1,827
Available for Sale, Gross Unrealized Losses	(335)	(738)
Available for Sale	15,845	21,787
Held to Maturity, Amortized Cost	12,000	12,000
Held to Maturity, Gross Unrealized Losses	(3,840)	(4,200)
Held to Maturity	8,160	7,800
Collateralized Mortgage Obligations [Member]
Marketable Securities [Line Items]
Available for Sale, Amortized Cost	198,180	321,881
Available for Sale, Gross Unrealized Gains		967
Available for Sale, Gross Unrealized Losses	(3,374)	(2,804)
Available for Sale	194,806	320,044
Held to Maturity, Amortized Cost	256,216	263,250
Held to Maturity, Gross Unrealized Losses	(25,076)	(20,864)
Held to Maturity	231,140	242,386
Mortgage-backed Securities [Member]
Marketable Securities [Line Items]
Available for Sale, Amortized Cost	105,723	97,779
Available for Sale, Gross Unrealized Gains	58	96
Available for Sale, Gross Unrealized Losses	(1,132)	(1,118)
Available for Sale	104,649	96,757
Held to Maturity, Amortized Cost	11,598,232	11,965,930
Held to Maturity, Gross Unrealized Gains	388	2,131
Held to Maturity, Gross Unrealized Losses	(1,477,027)	(1,357,283)
Held to Maturity	10,121,593	10,610,778
U.S. Treasury Securities and Obligations of U.S. Government Agencies [Member]
Marketable Securities [Line Items]
Held to Maturity, Amortized Cost	7,691	7,631
Held to Maturity, Gross Unrealized Losses	(107)	(52)
Held to Maturity	7,584	7,579
States and Political Subdivisions [Member]
Marketable Securities [Line Items]
Held to Maturity, Amortized Cost	111,699	116,497
Held to Maturity, Gross Unrealized Gains	764	1,864
Held to Maturity, Gross Unrealized Losses	(2,581)	(2,306)
Held to Maturity	$ 109,882	$ 116,055

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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Amortized cost of 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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Amount, before allowance for credit loss, of investment in debt security measured at amortized cost (held-to-maturity).

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

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