Investment Securities, AFS and HTM Securities Gross Unrealized Losses (Details) $ in Thousands	Sep. 30, 2021 USD ($) security	Dec. 31, 2020 USD ($) security
Investment securities AFS
Unrealized losses on available for sale securities, less than 12 months	$ (16,482)	$ (685)
Unrealized losses on available for sale securities, 12 months or more	(395)	(2,885)
Total unrealized losses on available for sale securities	(16,877)	(3,570)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	1,706,729	371,400
Fair value of unrealized losses on available for sale securities, less than 12 months	1,637,498	192,720
Fair value of unrealized losses on available for sale securities, 12 months or more	69,231	178,681
Total fair value of unrealized losses on available for sale securities	$ 1,706,729	$ 371,400
Available-for-sale, Number of Securities
Available for sale, number of securities, less than 12 months | security	60	27
Available for sale, number of securities, 12 months or more | security	17	16
Investment securities HTM
Unrealized losses on held to maturity securities, less than 12 months	$ (8,019)	$ 0
Unrealized losses on held to maturity securities, 12 months or more	0	0
Total unrealized losses on held to maturity securities	$ (8,019)	$ 0
Held-to-maturity, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, 12 Months or Longer | security	0	0
Fair value of unrealized losses on held to maturity securities, less than 12 months	$ 313,096	$ 325
Fair value of unrealized losses on held to maturity securities, 12 months or more	0	0
Total fair value of unrealized losses on held to maturity securities	$ 313,096	$ 325
Held-to-maturity, Securities In Unrealized Loss Positions Qualitative Disclosure Number Of Positions, less than 12 Months | security	74	1
US Treasury Securities
Investment securities AFS
Unrealized losses on available for sale securities, less than 12 months	$ (319)
Unrealized losses on available for sale securities, 12 months or more	0
Total unrealized losses on available for sale securities	(319)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	84,071
Fair value of unrealized losses on available for sale securities, less than 12 months	84,071
Fair value of unrealized losses on available for sale securities, 12 months or more	0
Total fair value of unrealized losses on available for sale securities	$ 84,071
Available-for-sale, Number of Securities
Available for sale, number of securities, less than 12 months | security	4
Available for sale, number of securities, 12 months or more | security	0
Agency Securities
Investment securities AFS
Unrealized losses on available for sale securities, less than 12 months	$ (2)
Unrealized losses on available for sale securities, 12 months or more	0
Total unrealized losses on available for sale securities	(2)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	14,998
Fair value of unrealized losses on available for sale securities, less than 12 months	14,998
Fair value of unrealized losses on available for sale securities, 12 months or more	0
Total fair value of unrealized losses on available for sale securities	$ 14,998
Available-for-sale, Number of Securities
Available for sale, number of securities, less than 12 months | security	1
Available for sale, number of securities, 12 months or more | security	0
US States and Political Subdivisions Debt Securities [Member]
Investment securities HTM
Unrealized losses on held to maturity securities, less than 12 months	$ (3,996)
Unrealized losses on held to maturity securities, 12 months or more	0
Total unrealized losses on held to maturity securities	(3,996)
Fair value of unrealized losses on held to maturity securities, less than 12 months	151,216
Fair value of unrealized losses on held to maturity securities, 12 months or more	0
Total fair value of unrealized losses on held to maturity securities	$ 151,216
US States and Political Subdivisions Debt Securities [Member] | Held to maturity, number of securities, less than 12 months
Investment securities HTM
Number of held to maturity securities in a continuous unrealized loss position | security	62
US States and Political Subdivisions Debt Securities [Member] | Held to maturity, number of securities, 12 months or more
Investment securities HTM
Number of held to maturity securities in a continuous unrealized loss position | security	0
Federal Family Education Loan Program (FFELP) Guaranteed Loans [Member]
Investment securities AFS
Unrealized losses on available for sale securities, less than 12 months	$ (124)	$ (129)
Unrealized losses on available for sale securities, 12 months or more	(347)	(2,885)
Total unrealized losses on available for sale securities	(471)	(3,013)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	99,878	187,948
Fair value of unrealized losses on available for sale securities, less than 12 months	34,876	9,267
Fair value of unrealized losses on available for sale securities, 12 months or more	65,002	178,681
Total fair value of unrealized losses on available for sale securities	$ 99,878	$ 187,948
Available-for-sale, Number of Securities
Available for sale, number of securities, less than 12 months | security	1	1
Available for sale, number of securities, 12 months or more | security	8	16
US Government-sponsored Enterprises Debt Securities [Member]
Investment securities AFS
Unrealized losses on available for sale securities, less than 12 months	$ 0	$ (53)
Unrealized losses on available for sale securities, 12 months or more	(48)	0
Total unrealized losses on available for sale securities	(48)	(53)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	4,229	8,379
Fair value of unrealized losses on available for sale securities, less than 12 months	0	8,379
Fair value of unrealized losses on available for sale securities, 12 months or more	4,229	0
Total fair value of unrealized losses on available for sale securities	$ 4,229	$ 8,379
Available-for-sale, Number of Securities
Available for sale, number of securities, less than 12 months | security	0	14
Available for sale, number of securities, 12 months or more | security	9	0
Other Debt securities
Investment securities AFS
Unrealized losses on available for sale securities, less than 12 months	$ (1)	$ 0
Unrealized losses on available for sale securities, 12 months or more	0	0
Total unrealized losses on available for sale securities	(1)	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	999	2,000
Fair value of unrealized losses on available for sale securities, less than 12 months	999	2,000
Fair value of unrealized losses on available for sale securities, 12 months or more	0	0
Total fair value of unrealized losses on available for sale securities	$ 999	$ 2,000
Available-for-sale, Number of Securities
Available for sale, number of securities, less than 12 months | security	1	2
Available for sale, number of securities, 12 months or more | security	0	0
FNMA/FHLMC | Residential Related Securities
Investment securities AFS
Unrealized losses on available for sale securities, less than 12 months	$ (9,144)	$ (500)
Unrealized losses on available for sale securities, 12 months or more	0	0
Total unrealized losses on available for sale securities	(9,144)	(500)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	1,170,981	163,002
Fair value of unrealized losses on available for sale securities, less than 12 months	1,170,981	163,002
Fair value of unrealized losses on available for sale securities, 12 months or more	0	0
Total fair value of unrealized losses on available for sale securities	$ 1,170,981	$ 163,002
Available-for-sale, Number of Securities
Available for sale, number of securities, less than 12 months | security	33	7
Available for sale, number of securities, 12 months or more | security	0	0
FNMA/FHLMC | Commercial mortgage-related securities
Investment securities AFS
Unrealized losses on available for sale securities, less than 12 months	$ (6,892)
Unrealized losses on available for sale securities, 12 months or more	0
Total unrealized losses on available for sale securities	(6,892)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	331,504
Fair value of unrealized losses on available for sale securities, less than 12 months	331,504
Fair value of unrealized losses on available for sale securities, 12 months or more	0
Total fair value of unrealized losses on available for sale securities	$ 331,504
Available-for-sale, Number of Securities
Available for sale, number of securities, less than 12 months | security	19
Available for sale, number of securities, 12 months or more | security	0
Investment securities HTM
Unrealized losses on held to maturity securities, less than 12 months	$ (4,002)
Unrealized losses on held to maturity securities, 12 months or more	0
Total unrealized losses on held to maturity securities	(4,002)
Fair value of unrealized losses on held to maturity securities, less than 12 months	146,248
Fair value of unrealized losses on held to maturity securities, 12 months or more	0
Total fair value of unrealized losses on held to maturity securities	$ 146,248
FNMA/FHLMC | Commercial mortgage-related securities | Held to maturity, number of securities, less than 12 months
Investment securities HTM
Number of held to maturity securities in a continuous unrealized loss position | security	11
FNMA/FHLMC | Commercial mortgage-related securities | Held to maturity, number of securities, 12 months or more
Investment securities HTM
Number of held to maturity securities in a continuous unrealized loss position | security	0
Government National Mortgage Association (GNMA) [Member] | Residential Related Securities
Investment securities AFS
Unrealized losses on available for sale securities, less than 12 months	$ 0	$ (3)
Unrealized losses on available for sale securities, 12 months or more	0	0
Total unrealized losses on available for sale securities	0	(3)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	69	9,784
Fair value of unrealized losses on available for sale securities, less than 12 months	69	9,784
Fair value of unrealized losses on available for sale securities, 12 months or more	0	0
Total fair value of unrealized losses on available for sale securities	$ 69	$ 9,784
Available-for-sale, Number of Securities
Available for sale, number of securities, less than 12 months | security	1	2
Available for sale, number of securities, 12 months or more | security	0	0
Investment securities HTM
Unrealized losses on held to maturity securities, less than 12 months		$ 0
Unrealized losses on held to maturity securities, 12 months or more		0
Total unrealized losses on held to maturity securities		0
Fair value of unrealized losses on held to maturity securities, less than 12 months		325
Fair value of unrealized losses on held to maturity securities, 12 months or more		0
Total fair value of unrealized losses on held to maturity securities		$ 325
Government National Mortgage Association (GNMA) [Member] | Residential Related Securities | Held to maturity, number of securities, less than 12 months
Investment securities HTM
Number of held to maturity securities in a continuous unrealized loss position | security		1
Government National Mortgage Association (GNMA) [Member] | Residential Related Securities | Held to maturity, number of securities, 12 months or more
Investment securities HTM
Number of held to maturity securities in a continuous unrealized loss position | security		0
Government National Mortgage Association (GNMA) [Member] | Commercial mortgage-related securities
Investment securities AFS
Unrealized losses on available for sale securities, less than 12 months		$ 0
Unrealized losses on available for sale securities, 12 months or more		0
Total unrealized losses on available for sale securities		0
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		287
Fair value of unrealized losses on available for sale securities, less than 12 months		287
Fair value of unrealized losses on available for sale securities, 12 months or more		0
Total fair value of unrealized losses on available for sale securities		$ 287
Available-for-sale, Number of Securities
Available for sale, number of securities, less than 12 months | security		1
Available for sale, number of securities, 12 months or more | security		0
Investment securities HTM
Unrealized losses on held to maturity securities, less than 12 months	$ (22)
Unrealized losses on held to maturity securities, 12 months or more	0
Total unrealized losses on held to maturity securities	(22)
Fair value of unrealized losses on held to maturity securities, less than 12 months	15,631
Fair value of unrealized losses on held to maturity securities, 12 months or more	0
Total fair value of unrealized losses on held to maturity securities	$ 15,631
Government National Mortgage Association (GNMA) [Member] | Commercial mortgage-related securities | Held to maturity, number of securities, less than 12 months
Investment securities HTM
Number of held to maturity securities in a continuous unrealized loss position | security	1
Government National Mortgage Association (GNMA) [Member] | Commercial mortgage-related securities | Held to maturity, number of securities, 12 months or more
Investment securities HTM
Number of held to maturity securities in a continuous unrealized loss position | security	0