Investment Securities, AFS and HTM Contractual Maturities (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Amortized Cost
Available for Sale, Due in one year or less	$ 6,773
Available for Sale, Due after one year through five years	179,763
Available for Sale, Due after five years through ten years	150,181
Available for Sale, Due after ten years	36,434
Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Amortized Cost	373,151
Available for Sale, Total debt securities	3,600,137	$ 2,997,032
Fair Value
Available for Sale, Due in one year or less	6,768
Available for Sale, Due after one year through five years	165,292
Available for Sale, Due after five years through ten years	149,003
Available for Sale, Due after ten years	36,229
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Fair Value	357,292
Available for Sale, Total debt securities	$ 3,381,607	2,742,025
Available for Sale, Ratio of Fair Value to Amortized Cost	93.90%
Amortized Cost
Held to Maturity, Due in one year or less	$ 14,358
Held to Maturity, Due after one year through five years	36,046
Held to Maturity, Due after five years through ten years	161,217
Held to Maturity, Due after ten years	1,509,554
Held to Maturity, Total Debt Securities	1,721,175
Held to Maturity, Amortized Cost	3,967,083	3,960,451
Fair Value
Held to Maturity, Due in one year or less	14,350
Held to Maturity, Due after one year through five years	35,926
Held to Maturity, Due after five years through ten years	159,591
Held to Maturity, Due after ten years	1,369,602
Held to Maturity, Securities, Debt Securities	1,579,468
Held to Maturity, Total debt securities at fair value	$ 3,481,502	3,401,018
Held to Maturity, Ratio of Fair Value to Amortized Cost	87.80%
Mortgage-backed Securities, Issued by Private Enterprises [Member]
Amortized Cost
Available for Sale, Total debt securities	$ 0
Fair Value
Available for Sale, Total debt securities	0
Amortized Cost
Held to Maturity, Amortized Cost	361,170	364,728
Fair Value
Held to Maturity, Total debt securities at fair value	301,265	303,505
Federal Family Education Loan Program (FFELP) Guaranteed Loans [Member]
Amortized Cost
Available for Sale, Total debt securities	147,876	157,138
Fair Value
Available for Sale, Total debt securities	143,084	151,191
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	4,020	4,512
Fair Value
Available for Sale, Total debt securities	3,983	4,477
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	1,768,846	1,820,642
Fair Value
Available for Sale, Total debt securities	1,574,578	1,604,610
Amortized Cost
Held to Maturity, Amortized Cost	981,065	961,231
Fair Value
Held to Maturity, Total debt securities at fair value	847,835	816,771
FNMA/FHLMC \| Commercial mortgage-related securities
Amortized Cost
Available for Sale, Total debt securities	18,952	19,038
Fair Value
Available for Sale, Total debt securities	17,618	17,142
Amortized Cost
Held to Maturity, Amortized Cost	785,516	778,796
Fair Value
Held to Maturity, Total debt securities at fair value	643,803	615,839
Government National Mortgage Association (GNMA) [Member] \| Residential Related Securities
Amortized Cost
Available for Sale, Total debt securities	1,092,742	502,537
Fair Value
Available for Sale, Total debt securities	1,095,588	497,596
Amortized Cost
Held to Maturity, Amortized Cost	53,298	52,979
Fair Value
Held to Maturity, Total debt securities at fair value	50,596	49,628
Government National Mortgage Association (GNMA) [Member] \| Commercial mortgage-related securities
Amortized Cost
Available for Sale, Total debt securities	194,550	115,031
Fair Value
Available for Sale, Total debt securities	189,466	110,462
Amortized Cost
Held to Maturity, Amortized Cost	64,859	69,369
Fair Value
Held to Maturity, Total debt securities at fair value	$ 58,536	$ 62,691

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