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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

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