Investment Securities, AFS and HTM Securities Amortized Costs and Fair Values (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2023	Dec. 31, 2022
Schedule of Available-for-sale and Held-to-maturity Securities [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	$ 3,772,373	$ 2,997,032
Debt Securities, Available-for-sale, Unrealized Gain	392	830
Debt Securities, Available-for-sale, Unrealized Loss	(267,987)	(255,837)
AFS investment securities, at fair value	3,504,777	2,742,025
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	3,939,001	3,960,451
Held-to-maturity, Gross Unrealized Gains	56,368	60,978
Held-to-maturity, Gross Unrealized Loss	(593,278)	(620,411)
Held-to-maturity, Fair Value	3,402,092	3,401,018
US Treasury Securities
Schedule of Available-for-sale and Held-to-maturity Securities [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	124,516	124,441
Debt Securities, Available-for-sale, Unrealized Gain	0	0
Debt Securities, Available-for-sale, Unrealized Loss	(14,563)	(15,063)
AFS investment securities, at fair value	109,954	109,378
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	999	999
Held-to-maturity, Gross Unrealized Gains	0	0
Held-to-maturity, Gross Unrealized Loss	(59)	(62)
Held-to-maturity, Fair Value	940	936
Agency Securities
Schedule of Available-for-sale and Held-to-maturity Securities [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	15,000	15,000
Debt Securities, Available-for-sale, Unrealized Gain	0	0
Debt Securities, Available-for-sale, Unrealized Loss	(1,483)	(1,468)
AFS investment securities, at fair value	13,517	13,532
US States and Political Subdivisions Debt Securities [Member]
Schedule of Available-for-sale and Held-to-maturity Securities [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	227,928	235,693
Debt Securities, Available-for-sale, Unrealized Gain	75	96
Debt Securities, Available-for-sale, Unrealized Loss	(5,515)	(5,074)
AFS investment securities, at fair value	222,487	230,714
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	1,713,510	1,732,351
Held-to-maturity, Gross Unrealized Gains	1,978	1,994
Held-to-maturity, Gross Unrealized Loss	(162,587)	(182,697)
Held-to-maturity, Fair Value	1,552,901	1,551,647
Mortgage-backed Securities, Issued by Private Enterprises [Member]
Schedule of Available-for-sale and Held-to-maturity Securities [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	0
AFS investment securities, at fair value	0
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	355,442	364,728
Held-to-maturity, Gross Unrealized Gains	10,734	11,697
Held-to-maturity, Gross Unrealized Loss	(72,395)	(72,920)
Held-to-maturity, Fair Value	293,782	303,505
Federal Family Education Loan Program (FFELP) Guaranteed Loans [Member]
Schedule of Available-for-sale and Held-to-maturity Securities [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	144,376	157,138
Debt Securities, Available-for-sale, Unrealized Gain	0	0
Debt Securities, Available-for-sale, Unrealized Loss	(4,211)	(5,947)
AFS investment securities, at fair value	140,166	151,191
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	0
Held-to-maturity, Fair Value	0
US Government-sponsored Enterprises Debt Securities [Member]
Schedule of Available-for-sale and Held-to-maturity Securities [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	3,757	4,512
Debt Securities, Available-for-sale, Unrealized Gain	11	15
Debt Securities, Available-for-sale, Unrealized Loss	(47)	(51)
AFS investment securities, at fair value	3,721	4,477
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	0
Held-to-maturity, Fair Value	0
Other Debt securities
Schedule of Available-for-sale and Held-to-maturity Securities [Line Items]
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	(87)	(78)
AFS investment securities, at fair value	2,913	2,922
FNMA/FHLMC | Residential Related Securities
Schedule of Available-for-sale and Held-to-maturity Securities [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	1,734,097	1,820,642
Debt Securities, Available-for-sale, Unrealized Gain	108	404
Debt Securities, Available-for-sale, Unrealized Loss	(213,265)	(216,436)
AFS investment securities, at fair value	1,520,939	1,604,610
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	969,503	961,231
Held-to-maturity, Gross Unrealized Gains	29,137	31,301
Held-to-maturity, Gross Unrealized Loss	(171,849)	(175,760)
Held-to-maturity, Fair Value	826,791	816,771
FNMA/FHLMC | Commercial mortgage-related securities
Schedule of Available-for-sale and Held-to-maturity Securities [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	18,866	19,038
Debt Securities, Available-for-sale, Unrealized Gain	0	0
Debt Securities, Available-for-sale, Unrealized Loss	(1,772)	(1,896)
AFS investment securities, at fair value	17,095	17,142
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	784,327	778,796
Held-to-maturity, Gross Unrealized Gains	14,008	15,324
Held-to-maturity, Gross Unrealized Loss	(174,942)	(178,281)
Held-to-maturity, Fair Value	623,393	615,839
Government National Mortgage Association (GNMA) [Member] | Residential Related Securities
Schedule of Available-for-sale and Held-to-maturity Securities [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	1,309,202	502,537
Debt Securities, Available-for-sale, Unrealized Gain	198	314
Debt Securities, Available-for-sale, Unrealized Loss	(18,761)	(5,255)
AFS investment securities, at fair value	1,290,640	497,596
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	52,260	52,979
Held-to-maturity, Gross Unrealized Gains	48	85
Held-to-maturity, Gross Unrealized Loss	(3,500)	(3,436)
Held-to-maturity, Fair Value	48,808	49,628
Government National Mortgage Association (GNMA) [Member] | Commercial mortgage-related securities
Schedule of Available-for-sale and Held-to-maturity Securities [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	191,630	115,031
Debt Securities, Available-for-sale, Unrealized Gain	0	0
Debt Securities, Available-for-sale, Unrealized Loss	(8,284)	(4,569)
AFS investment securities, at fair value	183,346	110,462
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	62,961	69,369
Held-to-maturity, Gross Unrealized Gains	461	577
Held-to-maturity, Gross Unrealized Loss	(7,946)	(7,254)
Held-to-maturity, Fair Value	$ 55,477	$ 62,691