Investment Securities, AFS and HTM Contractual Maturities (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Amortized Cost
Available for Sale, Due in one year or less	$ 9,023
Available for Sale, Due after one year through five years	105,078
Available for Sale, Due after five years through ten years	347,517
Available for Sale, Due after ten years	37,325
Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Amortized Cost	498,943
Available for Sale, Total debt securities	2,762,393	$ 4,338,671
Fair Value
Available for Sale, Due in one year or less	9,000
Available for Sale, Due after one year through five years	97,875
Available for Sale, Due after five years through ten years	323,983
Available for Sale, Due after ten years	34,656
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Fair Value	465,514
Available for Sale, Total debt securities	$ 2,487,312	4,332,015
Available for Sale, Ratio of Fair Value to Amortized Cost	90.00%
Amortized Cost
Held to Maturity, Due in one year or less	$ 16,969
Held to Maturity, Due after one year through five years	32,282
Held to Maturity, Due after five years through ten years	164,216
Held to Maturity, Due after ten years	1,524,666
Held to Maturity, Total Debt Securities	1,738,134
Held to Maturity, Amortized Cost	3,951,553	2,239,003
Fair Value
Held to Maturity, Due in one year or less	16,931
Held to Maturity, Due after one year through five years	31,668
Held to Maturity, Due after five years through ten years	157,427
Held to Maturity, Due after ten years	1,259,955
Held to Maturity, Securities, Debt Securities	1,465,980
Held to Maturity, Total debt securities at fair value	$ 3,295,760	2,348,664
Held to Maturity, Ratio of Fair Value to Amortized Cost	83.40%
Mortgage-backed Securities, Issued by Private Enterprises [Member]
Amortized Cost
Available for Sale, Total debt securities	$ 0	332,028
Fair Value
Available for Sale, Total debt securities	0	329,724
Amortized Cost
Held to Maturity, Amortized Cost	369,711
Fair Value
Held to Maturity, Total debt securities at fair value	306,972
Federal Family Education Loan Program (FFELP) Guaranteed Loans [Member]
Amortized Cost
Available for Sale, Total debt securities	163,314	177,974
Fair Value
Available for Sale, Total debt securities	158,556	177,325
Amortized Cost
Held to Maturity, Amortized Cost	0
Fair Value
Held to Maturity, Total debt securities at fair value	0
US Government-sponsored Enterprises Debt Securities [Member]
Amortized Cost
Available for Sale, Total debt securities	4,797	6,594
Fair Value
Available for Sale, Total debt securities	4,772	6,580
Amortized Cost
Held to Maturity, Amortized Cost	0
Fair Value
Held to Maturity, Total debt securities at fair value	0
FNMA/FHLMC \| Residential Related Securities
Amortized Cost
Available for Sale, Total debt securities	1,882,668	2,709,399
Fair Value
Available for Sale, Total debt securities	1,656,061	2,691,879
Amortized Cost
Held to Maturity, Amortized Cost	961,946	34,347
Fair Value
Held to Maturity, Total debt securities at fair value	812,099	36,139
FNMA/FHLMC \| Commercial mortgage-related securities
Amortized Cost
Available for Sale, Total debt securities	19,123	357,240
Fair Value
Available for Sale, Total debt securities	17,286	350,623
Amortized Cost
Held to Maturity, Amortized Cost	762,377	425,937
Fair Value
Held to Maturity, Total debt securities at fair value	601,600	419,400
Government National Mortgage Association (GNMA) [Member] \| Residential Related Securities
Amortized Cost
Available for Sale, Total debt securities	82,263	66,189
Fair Value
Available for Sale, Total debt securities	78,029	67,780
Amortized Cost
Held to Maturity, Amortized Cost	43,168	48,053
Fair Value
Held to Maturity, Total debt securities at fair value	39,323	49,631
Government National Mortgage Association (GNMA) [Member] \| Commercial mortgage-related securities
Amortized Cost
Available for Sale, Total debt securities	111,286	165,439
Fair Value
Available for Sale, Total debt securities	107,094	166,799
Amortized Cost
Held to Maturity, Amortized Cost	76,217	100,907
Fair Value
Held to Maturity, Total debt securities at fair value	$ 69,787	$ 102,506

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