Investment Securities, AFS and HTM Securities Amortized Costs and Fair Values (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2023	Dec. 31, 2022
AFS investment securities
Debt Securities, Available-for-sale, Amortized Cost	$ 3,749,814	$ 2,997,032
Debt Securities, Available-for-sale, Unrealized Gain	24,579	830
Debt Securities, Available-for-sale, Unrealized Loss	(173,501)	(255,837)
Debt Securities, Available-for-sale	3,600,892	2,742,025
HTM investment securities
Investment securities held to maturity	3,860,235	3,960,451
Gross Unrealized Gains	55,619	60,978
Held-to-maturity, Gross Unrealized Loss	(535,230)	(620,411)
Fair Value	3,380,624	3,401,018
US Treasury Securities [Member]
AFS investment securities
Debt Securities, Available-for-sale, Amortized Cost	39,984	124,441
Debt Securities, Available-for-sale, Unrealized Gain	0	0
Debt Securities, Available-for-sale, Unrealized Loss	(4,083)	(15,063)
Debt Securities, Available-for-sale	35,902	109,378
HTM investment securities
Investment securities held to maturity	999	999
Gross Unrealized Gains	0	0
Held-to-maturity, Gross Unrealized Loss	(36)	(62)
Fair Value	963	936
Agency Securities [Member]
AFS investment securities
Debt Securities, Available-for-sale, Amortized Cost		15,000
Debt Securities, Available-for-sale, Unrealized Gain		0
Debt Securities, Available-for-sale, Unrealized Loss		(1,468)
Debt Securities, Available-for-sale		13,532
US States and Political Subdivisions Debt Securities [Member]
AFS investment securities
Debt Securities, Available-for-sale, Amortized Cost	94,008	235,693
Debt Securities, Available-for-sale, Unrealized Gain	23	96
Debt Securities, Available-for-sale, Unrealized Loss	(2,214)	(5,074)
Debt Securities, Available-for-sale	91,817	230,714
HTM investment securities
Investment securities held to maturity	1,682,473	1,732,351
Gross Unrealized Gains	5,638	1,994
Held-to-maturity, Gross Unrealized Loss	(134,053)	(182,697)
Fair Value	1,554,059	1,551,647
Residential Related Securities \| FNMA/FHLMC [Member]
AFS investment securities
Debt Securities, Available-for-sale, Amortized Cost	1,274,052	1,820,642
Debt Securities, Available-for-sale, Unrealized Gain	294	404
Debt Securities, Available-for-sale, Unrealized Loss	(153,552)	(216,436)
Debt Securities, Available-for-sale	1,120,794	1,604,610
HTM investment securities
Investment securities held to maturity	941,973	961,231
Gross Unrealized Gains	27,007	31,301
Held-to-maturity, Gross Unrealized Loss	(164,587)	(175,760)
Fair Value	804,393	816,771
Residential Related Securities \| Government National Mortgage Association (GNMA)
AFS investment securities
Debt Securities, Available-for-sale, Amortized Cost	2,021,242	502,537
Debt Securities, Available-for-sale, Unrealized Gain	24,254	314
Debt Securities, Available-for-sale, Unrealized Loss	(2,822)	(5,255)
Debt Securities, Available-for-sale	2,042,675	497,596
HTM investment securities
Investment securities held to maturity	48,979	52,979
Gross Unrealized Gains	92	85
Held-to-maturity, Gross Unrealized Loss	(2,901)	(3,436)
Fair Value	46,170	49,628
Mortgage-Backed Securities, Issued by Private Enterprises [Member]
AFS investment securities
Debt Securities, Available-for-sale, Amortized Cost	0
Debt Securities, Available-for-sale	0
HTM investment securities
Investment securities held to maturity	345,083	364,728
Gross Unrealized Gains	9,796	11,697
Held-to-maturity, Gross Unrealized Loss	(65,372)	(72,920)
Fair Value	289,507	303,505
Commercial Mortgage-Backed Securities [Member] \| FNMA/FHLMC [Member]
AFS investment securities
Debt Securities, Available-for-sale, Amortized Cost	18,691	19,038
Debt Securities, Available-for-sale, Unrealized Gain	0	0
Debt Securities, Available-for-sale, Unrealized Loss	(1,755)	(1,896)
Debt Securities, Available-for-sale	16,937	17,142
HTM investment securities
Investment securities held to maturity	780,995	778,796
Gross Unrealized Gains	12,699	15,324
Held-to-maturity, Gross Unrealized Loss	(160,781)	(178,281)
Fair Value	632,914	615,839
Commercial Mortgage-Backed Securities [Member] \| Government National Mortgage Association (GNMA)
AFS investment securities
Debt Securities, Available-for-sale, Amortized Cost	161,928	115,031
Debt Securities, Available-for-sale, Unrealized Gain	0	0
Debt Securities, Available-for-sale, Unrealized Loss	(7,135)	(4,569)
Debt Securities, Available-for-sale	154,793	110,462
HTM investment securities
Investment securities held to maturity	59,733	69,369
Gross Unrealized Gains	386	577
Held-to-maturity, Gross Unrealized Loss	(7,500)	(7,254)
Fair Value	52,619	62,691
FFELP asset backed securities
AFS investment securities
Debt Securities, Available-for-sale, Amortized Cost	135,832	157,138
Debt Securities, Available-for-sale, Unrealized Gain	5	0
Debt Securities, Available-for-sale, Unrealized Loss	(1,862)	(5,947)
Debt Securities, Available-for-sale	133,975	151,191
HTM investment securities
Investment securities held to maturity	0
Fair Value	0
US Government-sponsored Enterprises Debt Securities [Member]
AFS investment securities
Debt Securities, Available-for-sale, Amortized Cost	1,077	4,512
Debt Securities, Available-for-sale, Unrealized Gain	2	15
Debt Securities, Available-for-sale, Unrealized Loss	(28)	(51)
Debt Securities, Available-for-sale	1,051	4,477
HTM investment securities
Investment securities held to maturity	0
Fair Value	0
Debt Securities [Member]
AFS investment securities
Debt Securities, Available-for-sale, Amortized Cost	3,000	3,000
Debt Securities, Available-for-sale, Unrealized Gain	0	0
Debt Securities, Available-for-sale, Unrealized Loss	(50)	(78)
Debt Securities, Available-for-sale	$ 2,950	$ 2,922

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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