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Securities (Debt securities) (Details) - USD ($) $ in Thousands | Mar. 31, 2022 | Dec. 31, 2021
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Debt Securities, [Line Items] |  |
Debt securities available-for-sale, amortized cost | $ 5,853,160 | $ 5,898,041
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 11,678 | 70,839
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | (337,467) | (57,881)
Debt securities available for sale at fair value | 5,527,371 | 5,910,999
Debt Securities, Held-to-Maturity, Amortized Cost | 2,202,437 | 2,148,327
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain | 0 | 50
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss | 164,400 | 25,771
Debt Securities, Held-to-maturity, Fair Value | 2,038,037 | 2,122,606
U.S. Government Agency and Government-Sponsored Enterprise Mortgage-Backed Securities and Collateralized Mortgage Obligations [Member] |  |
Debt Securities, [Line Items] |  |
Debt securities available-for-sale, amortized cost | 3,604,576 | 3,738,616
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 8,315 | 45,077
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | (205,237) | (38,092)
Debt securities available for sale at fair value | 3,407,654 | 3,745,601
Debt Securities, Held-to-Maturity, Amortized Cost | 2,202,437 | 2,148,327
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain | 0 | 50
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss | 164,400 | 25,771
Debt Securities, Held-to-maturity, Fair Value | 2,038,037 | 2,122,606
Asset-backed Securities [Member] |  |
Debt Securities, [Line Items] |  |
Debt securities available-for-sale, amortized cost | 433,879 | 469,052
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 377 | 3,802
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | (26,209) | (9,791)
Debt securities available for sale at fair value | 408,047 | 463,063
State and Municipal Securities [Member] |  |
Debt Securities, [Line Items] |  |
Debt securities available-for-sale, amortized cost | 1,002,490 | 983,704
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 2,275 | 18,525
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | (65,800) | (4,938)
Debt securities available for sale at fair value | 938,965 | 997,291
U.S. Government and Government-Sponsored Enterprise Securities [Member] |  |
Debt Securities, [Line Items] |  |
Debt securities available-for-sale, amortized cost | 247,727 | 252,755
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 711 | 3,095
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | (9,164) | (3,274)
Debt securities available for sale at fair value | 239,274 | 252,576
US Treasury Securities [Member] |  |
Debt Securities, [Line Items] |  |
Debt securities available-for-sale, amortized cost | 182,500 | 158,367
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 0 | 0
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | (9,158) | (831)
Debt securities available for sale at fair value | 173,342 | 157,536
Non-agency collateralized mortgage obligations [Member] |  |
Debt Securities, [Line Items] |  |
Debt securities available-for-sale, amortized cost | 381,988 | 295,547
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax | 0 | 340
Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax | (21,899) | (955)
Debt securities available for sale at fair value | $ 360,089 | $ 294,932

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