Investment Securities, AFS and HTM Securities Amortized Costs and Fair Values (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020
Investment securities AFS
Debt Securities, Available-for-sale, Amortized Cost	$ 4,338,671	$ 3,028,399
Debt Securities, Available-for-sale, Unrealized Gain	28,850	60,612
Debt Securities, Available-for-sale, Unrealized Loss	(35,506)	(3,570)
Debt Securities, Available-for-sale	541,305	3,085,441
Fair Value	4,332,015
Investment securities HTM
Investment securities held to maturity	2,239,003	1,879,005
Gross Unrealized Gains	118,471	149,938
Held-to-maturity, Gross Unrealized Loss	(8,809)	0
Fair Value	2,348,664	2,028,943
U.S. Treasury securities
Investment securities AFS
Debt Securities, Available-for-sale, Amortized Cost	124,291	26,436
Debt Securities, Available-for-sale, Unrealized Gain	0	95
Debt Securities, Available-for-sale, Unrealized Loss	(1,334)	0
Debt Securities, Available-for-sale	122,957	26,531
Investment securities HTM
Investment securities held to maturity	1,000	999
Gross Unrealized Gains	1	25
Held-to-maturity, Gross Unrealized Loss	0	0
Fair Value	1,001	1,024
Obligations of state and political subdivisions (municipal securities)
Investment securities AFS
Debt Securities, Available-for-sale, Amortized Cost	381,517	425,057
Debt Securities, Available-for-sale, Unrealized Gain	18,940	25,605
Debt Securities, Available-for-sale, Unrealized Loss	0	0
Debt Securities, Available-for-sale	400,457	450,662
Investment securities HTM
Investment securities held to maturity	1,628,759	1,441,900
Gross Unrealized Gains	113,179	133,544
Held-to-maturity, Gross Unrealized Loss	(1,951)	0
Fair Value	1,739,988	1,575,445
FFELP asset backed securities
Investment securities AFS
Debt Securities, Available-for-sale, Amortized Cost	177,974	329,030
Debt Securities, Available-for-sale, Unrealized Gain	475	1,172
Debt Securities, Available-for-sale, Unrealized Loss	(1,123)	(3,013)
Debt Securities, Available-for-sale	177,325	327,189
Investment securities HTM
Investment securities held to maturity	0
Fair Value	0
Fixed-income securities
Investment securities AFS
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	(6)	0
Debt Securities, Available-for-sale	2,994	3,000
Agency securities
Investment securities AFS
Debt Securities, Available-for-sale, Amortized Cost	15,000	24,985
Debt Securities, Available-for-sale, Unrealized Gain	0	53
Debt Securities, Available-for-sale, Unrealized Loss	(103)	0
Debt Securities, Available-for-sale	14,897	25,038
SBA
Investment securities AFS
Debt Securities, Available-for-sale, Amortized Cost	6,594	8,637
Debt Securities, Available-for-sale, Unrealized Gain	39	0
Debt Securities, Available-for-sale, Unrealized Loss	(54)	(53)
Debt Securities, Available-for-sale	6,580	8,584
Investment securities HTM
Investment securities held to maturity	0
Fair Value	0
Private-label
Investment securities AFS
Debt Securities, Available-for-sale, Amortized Cost	332,028
Debt Securities, Available-for-sale, Unrealized Gain	31
Debt Securities, Available-for-sale, Unrealized Loss	(2,335)
Debt Securities, Available-for-sale	329,724
Investment securities HTM
Investment securities held to maturity	0
Fair Value	0
FNMA/FHLMC [Member] \| Residential Related Securities
Investment securities AFS
Debt Securities, Available-for-sale, Amortized Cost	2,709,399	1,448,806
Debt Securities, Available-for-sale, Unrealized Gain	3,729	12,935
Debt Securities, Available-for-sale, Unrealized Loss	(21,249)	(500)
Debt Securities, Available-for-sale	2,691,879	1,461,241
Investment securities HTM
Investment securities held to maturity	34,347	54,599
Gross Unrealized Gains	1,792	2,891
Held-to-maturity, Gross Unrealized Loss	0	0
Fair Value	36,139	57,490
FNMA/FHLMC [Member] \| Commercial mortgage-related securities
Investment securities AFS
Debt Securities, Available-for-sale, Amortized Cost	357,240	19,654
Debt Securities, Available-for-sale, Unrealized Gain	2,686	3,250
Debt Securities, Available-for-sale, Unrealized Loss	(9,302)	0
Debt Securities, Available-for-sale	350,623	22,904
Investment securities HTM
Investment securities held to maturity	425,937	11,211
Gross Unrealized Gains	122	0
Held-to-maturity, Gross Unrealized Loss	(6,659)	0
Fair Value	419,400	11,211
GNMA \| Residential Related Securities
Investment securities AFS
Debt Securities, Available-for-sale, Amortized Cost	66,189	231,364
Debt Securities, Available-for-sale, Unrealized Gain	1,591	4,176
Debt Securities, Available-for-sale, Unrealized Loss	0	(3)
Debt Securities, Available-for-sale	67,780	235,537
Investment securities HTM
Investment securities held to maturity	48,053	114,553
Gross Unrealized Gains	1,578	4,260
Held-to-maturity, Gross Unrealized Loss	0	0
Fair Value	49,631	118,813
GNMA \| Commercial mortgage-related securities
Investment securities AFS
Debt Securities, Available-for-sale, Amortized Cost	165,439	511,429
Debt Securities, Available-for-sale, Unrealized Gain	1,360	13,327
Debt Securities, Available-for-sale, Unrealized Loss	0	0
Debt Securities, Available-for-sale	166,799	524,756
Investment securities HTM
Investment securities held to maturity	100,907	255,742
Gross Unrealized Gains	1,799	9,218
Held-to-maturity, Gross Unrealized Loss	(200)	0
Fair Value	$ 102,506	$ 264,960

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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