Investment Securities, AFS and HTM Securities Amortized Costs and Fair Values (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
Schedule of Available-for-sale and Held-to-maturity Securities [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	$ 2,890,763	$ 4,338,671
Debt Securities, Available-for-sale, Unrealized Gain	5,416	28,850
Debt Securities, Available-for-sale, Unrealized Loss	(115,376)	(35,506)
Debt Securities, Available-for-sale		4,332,015
Investment securities AFS, at fair value	2,780,803	4,332,015
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	3,939,920	2,239,003
Held-to-maturity, Gross Unrealized Gains	100,167	118,471
Held-to-maturity, Gross Unrealized Loss	(275,186)	(8,809)
Held-to-maturity, Fair Value	3,764,901	2,348,664
Fair Value, Inputs, Level 2
Schedule of Available-for-sale and Held-to-maturity Securities [Line Items]
Debt Securities, Available-for-sale	2,664,671	4,209,058
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	3,938,857	2,237,947
Held-to-maturity, Fair Value	3,763,872	2,347,608
Fair Value, Inputs, Level 2 | Fair Value, Measurements, Recurring | Other Debt securities
Schedule of Available-for-sale and Held-to-maturity Securities [Line Items]
Debt Securities, Available-for-sale	2,973	2,994
Fair Value, Inputs, Level 2 | Fair Value, Measurements, Recurring | 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	168,978	177,325
Fair Value, Inputs, Level 2 | Fair Value, Measurements, Recurring | US Government-sponsored Enterprises Debt Securities [Member]
Schedule of Available-for-sale and Held-to-maturity Securities [Line Items]
Debt Securities, Available-for-sale	5,845	6,580
Fair Value, Inputs, Level 1
Schedule of Available-for-sale and Held-to-maturity Securities [Line Items]
Debt Securities, Available-for-sale	116,132	122,957
FNMA/FHLMC | Fair Value, Inputs, Level 2 | Fair Value, Measurements, Recurring | Residential Related Securities
Schedule of Available-for-sale and Held-to-maturity Securities [Line Items]
Debt Securities, Available-for-sale	1,894,819	2,691,879
FNMA/FHLMC | Fair Value, Inputs, Level 2 | Fair Value, Measurements, Recurring | Commercial mortgage-related securities
Schedule of Available-for-sale and Held-to-maturity Securities [Line Items]
Debt Securities, Available-for-sale	19,786	350,623
Government National Mortgage Association (GNMA) [Member] | Fair Value, Inputs, Level 2 | Fair Value, Measurements, Recurring | Residential Related Securities
Schedule of Available-for-sale and Held-to-maturity Securities [Line Items]
Debt Securities, Available-for-sale	58,909	67,780
Government National Mortgage Association (GNMA) [Member] | Fair Value, Inputs, Level 2 | Fair Value, Measurements, Recurring | Commercial mortgage-related securities
Schedule of Available-for-sale and Held-to-maturity Securities [Line Items]
Debt Securities, Available-for-sale	126,760	166,799
US Treasury Securities [Member]
Schedule of Available-for-sale and Held-to-maturity Securities [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	124,328	124,291
Debt Securities, Available-for-sale, Unrealized Gain	0	0
Debt Securities, Available-for-sale, Unrealized Loss	(8,196)	(1,334)
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	998	1,000
Held-to-maturity, Gross Unrealized Gains	0	1
Held-to-maturity, Gross Unrealized Loss	(34)	0
Held-to-maturity, Fair Value	964	1,001
US Treasury Securities [Member] | Fair Value, Inputs, Level 2 | Fair Value, Measurements, Recurring
Schedule of Available-for-sale and Held-to-maturity Securities [Line Items]
Debt Securities, Available-for-sale		122,957
US Treasury Securities [Member] | Fair Value, Inputs, Level 1 | Fair Value, Measurements, Recurring
Schedule of Available-for-sale and Held-to-maturity Securities [Line Items]
Debt Securities, Available-for-sale	116,132	122,957
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	(800)	(103)
Agency Securities | Fair Value, Inputs, Level 2 | Fair Value, Measurements, Recurring
Schedule of Available-for-sale and Held-to-maturity Securities [Line Items]
Debt Securities, Available-for-sale	14,200	14,897
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	368,831	381,517
Debt Securities, Available-for-sale, Unrealized Gain	3,764	18,940
Debt Securities, Available-for-sale, Unrealized Loss	(195)	0
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	1,696,536	1,628,759
Held-to-maturity, Gross Unrealized Gains	32,201	113,179
Held-to-maturity, Gross Unrealized Loss	(80,896)	(1,951)
Held-to-maturity, Fair Value	1,647,842	1,739,988
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 2 | Fair Value, Measurements, Recurring
Schedule of Available-for-sale and Held-to-maturity Securities [Line Items]
Debt Securities, Available-for-sale	372,401	400,457
Residential Related Securities | FNMA/FHLMC
Schedule of Available-for-sale and Held-to-maturity Securities [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	1,993,893	2,709,399
Debt Securities, Available-for-sale, Unrealized Gain	937	3,729
Debt Securities, Available-for-sale, Unrealized Loss	(100,011)	(21,249)
Debt Securities, Available-for-sale	1,894,819
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	956,470	34,347
Held-to-maturity, Gross Unrealized Gains	35,739	1,792
Held-to-maturity, Gross Unrealized Loss	(72,418)	0
Held-to-maturity, Fair Value	919,790	36,139
Residential Related Securities | Government National Mortgage Association (GNMA) [Member]
Schedule of Available-for-sale and Held-to-maturity Securities [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	59,470	66,189
Debt Securities, Available-for-sale, Unrealized Gain	166	1,591
Debt Securities, Available-for-sale, Unrealized Loss	(726)	0
Debt Securities, Available-for-sale	58,909
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	44,742	48,053
Held-to-maturity, Gross Unrealized Gains	116	1,578
Held-to-maturity, Gross Unrealized Loss	(643)	0
Held-to-maturity, Fair Value	44,215	49,631
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	332,028
Debt Securities, Available-for-sale, Unrealized Gain		31
Debt Securities, Available-for-sale, Unrealized Loss		(2,335)
Debt Securities, Available-for-sale	0	329,724
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	384,016
Held-to-maturity, Gross Unrealized Gains	13,460
Held-to-maturity, Gross Unrealized Loss	(28,955)
Held-to-maturity, Fair Value	368,521
Mortgage-backed Securities, Issued by Private Enterprises [Member] | Residential Related Securities
Schedule of Available-for-sale and Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	384,016
Mortgage-backed Securities, Issued by Private Enterprises [Member] | Fair Value, Inputs, Level 2 | Fair Value, Measurements, Recurring
Schedule of Available-for-sale and Held-to-maturity Securities [Line Items]
Debt Securities, Available-for-sale	0	329,724
Commercial mortgage-related securities | FNMA/FHLMC
Schedule of Available-for-sale and Held-to-maturity Securities [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	19,290	357,240
Debt Securities, Available-for-sale, Unrealized Gain	496	2,686
Debt Securities, Available-for-sale, Unrealized Loss	0	(9,302)
Debt Securities, Available-for-sale	19,786
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	764,775	425,937
Held-to-maturity, Gross Unrealized Gains	17,620	122
Held-to-maturity, Gross Unrealized Loss	(88,784)	(6,659)
Held-to-maturity, Fair Value	693,610	419,400
Commercial mortgage-related securities | Government National Mortgage Association (GNMA) [Member]
Schedule of Available-for-sale and Held-to-maturity Securities [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	128,019	165,439
Debt Securities, Available-for-sale, Unrealized Gain	18	1,360
Debt Securities, Available-for-sale, Unrealized Loss	(1,278)	0
Debt Securities, Available-for-sale	126,760
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss	92,383	100,907
Held-to-maturity, Gross Unrealized Gains	1,032	1,799
Held-to-maturity, Gross Unrealized Loss	(3,456)	(200)
Held-to-maturity, Fair Value	89,959	102,506
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	173,068	177,974
Debt Securities, Available-for-sale, Unrealized Gain	0	475
Debt Securities, Available-for-sale, Unrealized Loss	(4,090)	(1,123)
Debt Securities, Available-for-sale	168,978
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	5,865	6,594
Debt Securities, Available-for-sale, Unrealized Gain	33	39
Debt Securities, Available-for-sale, Unrealized Loss	(53)	(54)
Debt Securities, Available-for-sale	5,845
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	$ (27)	$ (6)