Investment Securities Available for Sale - Amortized Cost And Estimated Fair Value By Contractual Maturity Of Investment Securities Available For Sale (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Amortized Cost
Within one year, amortized cost	$ 92,363
1 to 5 years, amortized cost	1,080,999
5 to 10 years, amortized cost	899,520
More than 10 years, amortized cost	9,079,861
Amortized Cost	11,152,743	$ 11,091,254
Fair Value
Within one year, fair value	92,673
1 to 5 years, fair value	1,071,486
5 to 10 years, fair value	874,949
More than 10 years, fair value	7,655,407
Total, fair value	9,694,515	9,788,662
U.S. Treasury securities
Amortized Cost
Within one year, amortized cost	25,923
1 to 5 years, amortized cost	258,854
5 to 10 years, amortized cost	331,260
More than 10 years, amortized cost	0
Amortized Cost	616,037	588,082
Fair Value
Within one year, fair value	25,923
1 to 5 years, fair value	258,488
5 to 10 years, fair value	330,998
More than 10 years, fair value	0
Total, fair value	615,409	597,629
U.S. Government agency securities
Amortized Cost
Within one year, amortized cost	0
1 to 5 years, amortized cost	29,993
5 to 10 years, amortized cost	0
More than 10 years, amortized cost	0
Amortized Cost	29,993	29,993
Fair Value
Within one year, fair value	0
1 to 5 years, fair value	28,783
5 to 10 years, fair value	0
More than 10 years, fair value	0
Total, fair value	28,783	28,940
Mortgage-backed securities issued by U.S. Government agencies
Amortized Cost
Within one year, amortized cost	0
1 to 5 years, amortized cost	60
5 to 10 years, amortized cost	3
More than 10 years, amortized cost	1,022,818
Amortized Cost	1,022,881	1,021,612
Fair Value
Within one year, fair value	0
1 to 5 years, fair value	58
5 to 10 years, fair value	3
More than 10 years, fair value	911,857
Total, fair value	911,918	925,664
Mortgage-backed securities issued by U.S. Government sponsored enterprises
Amortized Cost
Within one year, amortized cost	0
1 to 5 years, amortized cost	0
5 to 10 years, amortized cost	10,552
More than 10 years, amortized cost	7,372,853
Amortized Cost	7,383,405	7,523,399
Fair Value
Within one year, fair value	0
1 to 5 years, fair value	0
5 to 10 years, fair value	9,766
More than 10 years, fair value	6,173,145
Total, fair value	6,182,911	6,430,379
Collateralized mortgage obligations issued by U.S. Government agencies or sponsored enterprises
Amortized Cost
Within one year, amortized cost	0
1 to 5 years, amortized cost	41
5 to 10 years, amortized cost	9,865
More than 10 years, amortized cost	666,866
Amortized Cost	676,772	692,487
Fair Value
Within one year, fair value	0
1 to 5 years, fair value	40
5 to 10 years, fair value	9,491
More than 10 years, fair value	555,409
Total, fair value	564,940	587,595
Commercial mortgage-backed securities issued by U.S. Government agencies or sponsored enterprises
Amortized Cost
Within one year, amortized cost	66,440
1 to 5 years, amortized cost	783,017
5 to 10 years, amortized cost	547,840
More than 10 years, amortized cost	17,324
Amortized Cost	1,414,621	1,226,672
Fair Value
Within one year, fair value	66,750
1 to 5 years, fair value	775,293
5 to 10 years, fair value	524,691
More than 10 years, fair value	14,996
Total, fair value	1,381,730	1,209,783
Corporate debt securities and other debt securities
Amortized Cost
Within one year, amortized cost	0
1 to 5 years, amortized cost	9,034
5 to 10 years, amortized cost	0
More than 10 years, amortized cost	0
Amortized Cost	9,034	9,009
Fair Value
Within one year, fair value	0
1 to 5 years, fair value	8,824
5 to 10 years, fair value	0
More than 10 years, fair value	0
Total, fair value	$ 8,824	$ 8,672

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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