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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 | Dec. 31, 2021 | Dec. 31, 2020
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Amortized Cost |  |
Amortized cost, within one year | $ 545,074 |
Amortized cost, 1 to 5 years | 182,307 |
Amortized cost, 5 to 10 years | 452,953 |
Amortized cost, more than 10 years | 9,811,172 |
Amortized Cost | 10,991,506 | $ 7,801,864
Fair Value |  |
Fair value, within one year | 545,306 |
Fair value, 1 to 5 years | 184,013 |
Fair value, 5 to 10 years | 452,296 |
Fair value, more than 10 years | 9,736,714 |
Total fair value | 10,918,329 | 7,962,438
U.S. Treasury securities |  |
Amortized Cost |  |
Amortized cost, within one year | 20,600 |
Amortized cost, 1 to 5 years | 0 |
Amortized cost, 5 to 10 years | 99,865 |
Amortized cost, more than 10 years | 0 |
Amortized Cost | 120,465 | 20,257
Fair Value |  |
Fair value, within one year | 20,600 |
Fair value, 1 to 5 years | 0 |
Fair value, 5 to 10 years | 97,238 |
Fair value, more than 10 years | 0 |
Total fair value | 117,838 | 20,257
U.S. Government agency securities |  |
Amortized Cost |  |
Amortized cost, within one year | 756 |
Amortized cost, 1 to 5 years | 321 |
Amortized cost, 5 to 10 years | 52,137 |
Amortized cost, more than 10 years | 0 |
Amortized Cost | 53,214 | 79,638
Fair Value |  |
Fair value, within one year | 760 |
Fair value, 1 to 5 years | 322 |
Fair value, 5 to 10 years | 53,119 |
Fair value, more than 10 years | 0 |
Total fair value | 54,201 | 82,320
Mortgage-backed securities issued by U.S. Government agencies |  |
Amortized Cost |  |
Amortized cost, within one year | 0 |
Amortized cost, 1 to 5 years | 842 |
Amortized cost, 5 to 10 years | 131 |
Amortized cost, more than 10 years | 789,356 |
Amortized Cost | 790,329 | 1,216,012
Fair Value |  |
Fair value, within one year | 0 |
Fair value, 1 to 5 years | 870 |
Fair value, 5 to 10 years | 136 |
Fair value, more than 10 years | 778,627 |
Total fair value | 779,633 | 1,218,017
Mortgage-backed securities issued by U.S. Government sponsored enterprises |  |
Amortized Cost |  |
Amortized cost, within one year | 28 |
Amortized cost, 1 to 5 years | 0 |
Amortized cost, 5 to 10 years | 80,539 |
Amortized cost, more than 10 years | 7,983,323 |
Amortized Cost | 8,063,890 | 4,865,858
Fair Value |  |
Fair value, within one year | 28 |
Fair value, 1 to 5 years | 0 |
Fair value, 5 to 10 years | 83,271 |
Fair value, more than 10 years | 7,929,002 |
Total fair value | 8,012,301 | 5,000,046
Collateralized mortgage obligations issued by U.S. Government agencies or sponsored enterprises |  |
Amortized Cost |  |
Amortized cost, within one year | 0 |
Amortized cost, 1 to 5 years | 0 |
Amortized cost, 5 to 10 years | 146 |
Amortized cost, more than 10 years | 951,545 |
Amortized Cost | 951,691 | 1,245,644
Fair Value |  |
Fair value, within one year | 0 |
Fair value, 1 to 5 years | 0 |
Fair value, 5 to 10 years | 150 |
Fair value, more than 10 years | 939,473 |
Total fair value | 939,623 | 1,250,377
Commercial mortgage-backed securities issued by U.S. Government agencies or sponsored enterprises |  |
Amortized Cost |  |
Amortized cost, within one year | 0 |
Amortized cost, 1 to 5 years | 181,144 |
Amortized cost, 5 to 10 years | 211,328 |
Amortized cost, more than 10 years | 86,948 |
Amortized Cost | 479,420 | 354,244
Fair Value |  |
Fair value, within one year | 0 |
Fair value, 1 to 5 years | 182,821 |
Fair value, 5 to 10 years | 209,311 |
Fair value, more than 10 years | 89,612 |
Total fair value | 481,744 | 370,921
Asset-backed securities |  |
Amortized Cost |  |
Amortized cost, within one year | 514,188 |
Amortized cost, 1 to 5 years | 0 |
Amortized cost, 5 to 10 years | 0 |
Amortized cost, more than 10 years | 0 |
Amortized Cost | 514,188 |
Fair Value |  |
Fair value, within one year | 514,188 |
Fair value, 1 to 5 years | 0 |
Fair value, 5 to 10 years | 0 |
Fair value, more than 10 years | 0 |
Total fair value | 514,188 |
Corporate debt securities and other debt securities |  |
Amortized Cost |  |
Amortized cost, within one year | 9,502 |
Amortized cost, 1 to 5 years | 0 |
Amortized cost, 5 to 10 years | 8,807 |
Amortized cost, more than 10 years | 0 |
Amortized Cost | 18,309 | 20,211
Fair Value |  |
Fair value, within one year | 9,730 |
Fair value, 1 to 5 years | 0 |
Fair value, 5 to 10 years | 9,071 |
Fair value, more than 10 years | 0 |
Total fair value | $ 18,801 | $ 20,500

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