Investment Securities, AFS and HTM Expected Maturities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Amortized Cost
Due in one year or less	$ 6,799
Due after one year through five years	74,250
Due after five years through ten years	405,344
Due after ten years	37,416
Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Amortized Cost	523,808
Total debt securities	4,338,671	$ 3,028,399
Investment securities available for sale, amortized cost	4,338,671	3,028,399
Fair Value
Due in one year or less	6,809
Due after one year through five years	74,142
Due after five years through ten years	418,942
Due after ten years	41,412
Total debt securities, AFS Fair Value	541,305	3,085,441
Investment securities AFS, at fair value	$ 541,305	3,085,441
Ratio of Fair Value to Amortized Cost	99.80%
Amortized Cost
Due in one year or less	$ 34,646
Due after one year through five years	34,697
Due after five years through ten years	161,627
Due after ten years	1,398,789
Amortized Cost	2,239,003	1,879,005
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, Amortized Cost	1,629,759
Fair Value
Due in one year or less	34,842
Due after one year through five years	35,820
Due after five years through ten years	167,967
Due after ten years	1,502,359
Debt Securities, Held-to-maturity, Fair Value	$ 2,348,664	2,028,943
Ratio of Fair Value to Amortized Cost	104.90%
Debt Securities, Held-to-maturity, Maturity, Allocated and Single Maturity Date, Fair Value	$ 1,740,988
FFELP asset backed securities
Amortized Cost
Total debt securities	177,974	329,030
Investment securities available for sale, amortized cost	177,974	329,030
Fair Value
Total debt securities, AFS Fair Value	177,325	327,189
Investment securities AFS, at fair value	177,325	327,189
Amortized Cost
Amortized Cost	0
Fair Value
Debt Securities, Held-to-maturity, Fair Value	0
SBA
Amortized Cost
Total debt securities	6,594	8,637
Investment securities available for sale, amortized cost	6,594	8,637
Fair Value
Total debt securities, AFS Fair Value	6,580	8,584
Investment securities AFS, at fair value	6,580	8,584
Amortized Cost
Amortized Cost	0
Fair Value
Debt Securities, Held-to-maturity, Fair Value	0
Private-label
Amortized Cost
Total debt securities	332,028
Investment securities available for sale, amortized cost	332,028
Fair Value
Total debt securities, AFS Fair Value	329,724
Investment securities AFS, at fair value	329,724
Amortized Cost
Amortized Cost	0
Fair Value
Debt Securities, Held-to-maturity, Fair Value	0
FNMA/FHLMC [Member] \| Residential Related Securities
Amortized Cost
Total debt securities	2,709,399	1,448,806
Investment securities available for sale, amortized cost	2,709,399	1,448,806
Fair Value
Total debt securities, AFS Fair Value	2,691,879	1,461,241
Investment securities AFS, at fair value	2,691,879	1,461,241
Amortized Cost
Amortized Cost	34,347	54,599
Fair Value
Debt Securities, Held-to-maturity, Fair Value	36,139	57,490
FNMA/FHLMC [Member] \| Commercial mortgage-related securities
Amortized Cost
Total debt securities	357,240	19,654
Investment securities available for sale, amortized cost	357,240	19,654
Fair Value
Total debt securities, AFS Fair Value	350,623	22,904
Investment securities AFS, at fair value	350,623	22,904
Amortized Cost
Amortized Cost	425,937	11,211
Fair Value
Debt Securities, Held-to-maturity, Fair Value	419,400	11,211
GNMA \| Residential Related Securities
Amortized Cost
Total debt securities	66,189	231,364
Investment securities available for sale, amortized cost	66,189	231,364
Fair Value
Total debt securities, AFS Fair Value	67,780	235,537
Investment securities AFS, at fair value	67,780	235,537
Amortized Cost
Amortized Cost	48,053	114,553
Fair Value
Debt Securities, Held-to-maturity, Fair Value	49,631	118,813
GNMA \| Commercial mortgage-related securities
Amortized Cost
Total debt securities	165,439	511,429
Investment securities available for sale, amortized cost	165,439	511,429
Fair Value
Total debt securities, AFS Fair Value	166,799	524,756
Investment securities AFS, at fair value	166,799	524,756
Amortized Cost
Amortized Cost	100,907	255,742
Fair Value
Debt Securities, Held-to-maturity, Fair Value	$ 102,506	$ 264,960

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