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Investment Securities, AFS and HTM Contractual Maturities (Details) - USD ($) $ in Thousands | Mar. 31, 2022 | Dec. 31, 2021
--- | --- | ---
Amortized Cost |  |
Available for Sale, Due in one year or less | $ 5,167 |
Available for Sale, Due after one year through five years | 89,914 |
Available for Sale, Due after five years through ten years | 378,692 |
Available for Sale, Due after ten years | 37,386 |
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Fair Value | 505,706 |
Debt Securities, Available-for-sale, Maturity, without Single Maturity Date, Amortized Cost | 511,159 |
Available for Sale, Total debt securities | 2,890,763 | $ 4,338,671
Available for Sale, amortized cost | 2,890,763 | 4,338,671
Fair Value |  |
Available for Sale, Due in one year or less | 5,171 |
Available for Sale, Due after one year through five years | 87,185 |
Available for Sale, Due after five years through ten years | 374,733 |
Available for Sale, Due after ten years | $ 38,617 |
Available for Sale, Total debt securities |  | 4,332,015
Available for Sale, Ratio of Fair Value to Amortized Cost | 96.20% |
Investment securities AFS, at fair value | $ 2,780,803 | 4,332,015
Amortized Cost |  |
Held to Maturity, Due in one year or less | 18,432 |
Held to Maturity, Due after one year through five years | 34,156 |
Held to Maturity, Due after five years through ten years | 163,456 |
Held to Maturity, Due after ten years | 1,481,489 |
Held to Maturity, Total Debt Securities | 1,697,534 |
Held to Maturity, Amortized Cost | 3,939,920 | 2,239,003
Fair Value |  |
Held to Maturity, Due in one year or less | 18,503 |
Held to Maturity, Due after one year through five years | 34,343 |
Held to Maturity, Due after five years through ten years | 164,057 |
Held to Maturity, Due after ten years | 1,431,903 |
Held to Maturity, Securities, Debt Securities | 1,648,806 |
Held to Maturity, Total debt securities at fair value | $ 3,764,901 | 2,348,664
Held to Maturity, Ratio of Fair Value to Amortized Cost | 95.60% |
Residential Related Securities | FNMA/FHLMC |  |
Amortized Cost |  |
Available for Sale, Total debt securities | $ 1,993,893 | 2,709,399
Available for Sale, amortized cost | 1,993,893 | 2,709,399
Fair Value |  |
Available for Sale, Total debt securities | 1,894,819 |
Amortized Cost |  |
Held to Maturity, Amortized Cost | 956,470 | 34,347
Fair Value |  |
Held to Maturity, Total debt securities at fair value | 919,790 | 36,139
Residential Related Securities | Government National Mortgage Association (GNMA) [Member] |  |
Amortized Cost |  |
Available for Sale, Total debt securities | 59,470 | 66,189
Available for Sale, amortized cost | 59,470 | 66,189
Fair Value |  |
Available for Sale, Total debt securities | 58,909 |
Amortized Cost |  |
Held to Maturity, Amortized Cost | 44,742 | 48,053
Fair Value |  |
Held to Maturity, Total debt securities at fair value | 44,215 | 49,631
Commercial mortgage-related securities | FNMA/FHLMC |  |
Amortized Cost |  |
Available for Sale, Total debt securities | 19,290 | 357,240
Available for Sale, amortized cost | 19,290 | 357,240
Fair Value |  |
Available for Sale, Total debt securities | 19,786 |
Amortized Cost |  |
Held to Maturity, Amortized Cost | 764,775 | 425,937
Fair Value |  |
Held to Maturity, Total debt securities at fair value | 693,610 | 419,400
Commercial mortgage-related securities | Government National Mortgage Association (GNMA) [Member] |  |
Amortized Cost |  |
Available for Sale, Total debt securities | 128,019 | 165,439
Available for Sale, amortized cost | 128,019 | 165,439
Fair Value |  |
Available for Sale, Total debt securities | 126,760 |
Amortized Cost |  |
Held to Maturity, Amortized Cost | 92,383 | 100,907
Fair Value |  |
Held to Maturity, Total debt securities at fair value | 89,959 | 102,506
Federal Family Education Loan Program (FFELP) Guaranteed Loans [Member] |  |
Amortized Cost |  |
Available for Sale, Total debt securities | 173,068 | 177,974
Available for Sale, amortized cost | 173,068 | 177,974
Fair Value |  |
Available for Sale, Total debt securities | 168,978 |
Amortized Cost |  |
Held to Maturity, Amortized Cost | 0 |
Fair Value |  |
Held to Maturity, Total debt securities at fair value | 0 |
US Government-sponsored Enterprises Debt Securities [Member] |  |
Amortized Cost |  |
Available for Sale, Total debt securities | 5,865 | 6,594
Available for Sale, amortized cost | 5,865 | 6,594
Fair Value |  |
Available for Sale, Total debt securities | 5,845 |
Amortized Cost |  |
Held to Maturity, Amortized Cost | 0 |
Fair Value |  |
Held to Maturity, Total debt securities at fair value | 0 |
Mortgage-backed Securities, Issued by Private Enterprises [Member] |  |
Amortized Cost |  |
Available for Sale, Total debt securities | 0 | 332,028
Available for Sale, amortized cost | 0 | 332,028
Fair Value |  |
Available for Sale, Total debt securities | 0 | $ 329,724
Amortized Cost |  |
Held to Maturity, Amortized Cost | 384,016 |
Fair Value |  |
Held to Maturity, Total debt securities at fair value | $ 368,521 |

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