Investment Securities, AFS and HTM Securities Amortized Costs and Fair Values (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2023	Dec. 31, 2022
Schedule of Available-for-sale and Held-to-maturity Securities [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	$ 3,600,137	$ 2,997,032
Debt Securities, Available-for-sale, Unrealized Gain	7,854	830
Debt Securities, Available-for-sale, Unrealized Loss	(226,383)	(255,837)
AFS investment securities, at fair value	3,381,607	2,742,025
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	3,967,083	3,960,451
Held-to-maturity, Gross Unrealized Gains	61,768	60,978
Held-to-maturity, Gross Unrealized Loss	(547,349)	(620,411)
Held-to-maturity, Fair Value	3,481,502	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	124,478	124,441
Debt Securities, Available-for-sale, Unrealized Gain	0	0
Debt Securities, Available-for-sale, Unrealized Loss	(12,735)	(15,063)
AFS investment securities, at fair value	111,743	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	(51)	(62)
Held-to-maturity, Fair Value	947	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	(1,271)	(1,468)
AFS investment securities, at fair value	13,730	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	230,673	235,693
Debt Securities, Available-for-sale, Unrealized Gain	291	96
Debt Securities, Available-for-sale, Unrealized Loss	(2,063)	(5,074)
AFS investment securities, at fair value	228,902	230,714
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	1,720,177	1,732,351
Held-to-maturity, Gross Unrealized Gains	4,888	1,994
Held-to-maturity, Gross Unrealized Loss	(146,544)	(182,697)
Held-to-maturity, Fair Value	1,578,521	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	361,170	364,728
Held-to-maturity, Gross Unrealized Gains	11,242	11,697
Held-to-maturity, Gross Unrealized Loss	(71,147)	(72,920)
Held-to-maturity, Fair Value	301,265	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	147,876	157,138
Debt Securities, Available-for-sale, Unrealized Gain	0	0
Debt Securities, Available-for-sale, Unrealized Loss	(4,791)	(5,947)
AFS investment securities, at fair value	143,084	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	4,020	4,512
Debt Securities, Available-for-sale, Unrealized Gain	13	15
Debt Securities, Available-for-sale, Unrealized Loss	(50)	(51)
AFS investment securities, at fair value	3,983	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	(82)	(78)
AFS investment securities, at fair value	2,918	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	1,768,846	1,820,642
Debt Securities, Available-for-sale, Unrealized Gain	260	404
Debt Securities, Available-for-sale, Unrealized Loss	(194,529)	(216,436)
AFS investment securities, at fair value	1,574,578	1,604,610
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	981,065	961,231
Held-to-maturity, Gross Unrealized Gains	30,284	31,301
Held-to-maturity, Gross Unrealized Loss	(163,514)	(175,760)
Held-to-maturity, Fair Value	847,835	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	18,952	19,038
Debt Securities, Available-for-sale, Unrealized Gain	0	0
Debt Securities, Available-for-sale, Unrealized Loss	(1,335)	(1,896)
AFS investment securities, at fair value	17,618	17,142
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	785,516	778,796
Held-to-maturity, Gross Unrealized Gains	14,657	15,324
Held-to-maturity, Gross Unrealized Loss	(156,369)	(178,281)
Held-to-maturity, Fair Value	643,803	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	1,092,742	502,537
Debt Securities, Available-for-sale, Unrealized Gain	7,273	314
Debt Securities, Available-for-sale, Unrealized Loss	(4,427)	(5,255)
AFS investment securities, at fair value	1,095,588	497,596
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	53,298	52,979
Held-to-maturity, Gross Unrealized Gains	195	85
Held-to-maturity, Gross Unrealized Loss	(2,897)	(3,436)
Held-to-maturity, Fair Value	50,596	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	194,550	115,031
Debt Securities, Available-for-sale, Unrealized Gain	17	0
Debt Securities, Available-for-sale, Unrealized Loss	(5,101)	(4,569)
AFS investment securities, at fair value	189,466	110,462
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	64,859	69,369
Held-to-maturity, Gross Unrealized Gains	502	577
Held-to-maturity, Gross Unrealized Loss	(6,826)	(7,254)
Held-to-maturity, Fair Value	$ 58,536	$ 62,691