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Investment Securities Available for Sale (Schedule of Available for Sale Investment Securities) (Details) - USD ($) $ in Thousands | Sep. 30, 2023 | Dec. 31, 2022
--- | --- | ---
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | $ 11,174,755 | $ 11,273,327
Gross Unrealized Gains | 0 | 2,560
Gross Unrealized Losses | (1,937,564) | (1,597,784)
Fair Value | 9,237,191 | 9,678,103
U.S. Treasury securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 556,791 | 515,953
Gross Unrealized Gains | 0 | 0
Gross Unrealized Losses | (47,331) | (44,140)
Fair Value | 509,460 | 471,813
U.S. Government agency securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 52,140 | 52,411
Gross Unrealized Gains | 0 | 0
Gross Unrealized Losses | (4,634) | (3,613)
Fair Value | 47,506 | 48,798
Mortgage-backed securities issued by U.S. Government agencies |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 1,040,825 | 904,593
Gross Unrealized Gains | 0 | 1,624
Gross Unrealized Losses | (148,571) | (113,468)
Fair Value | 892,254 | 792,749
Mortgage-backed securities issued by U.S. Government sponsored enterprises |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 7,781,751 | 8,144,374
Gross Unrealized Gains | 0 | 936
Gross Unrealized Losses | (1,519,999) | (1,250,240)
Fair Value | 6,261,752 | 6,895,070
Collateralized mortgage obligations issued by U.S. Government agencies or sponsored enterprises |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 710,600 | 769,498
Gross Unrealized Gains | 0 | 0
Gross Unrealized Losses | (131,764) | (114,371)
Fair Value | 578,836 | 655,127
Commercial mortgage-backed securities issued by U.S. Government agencies or sponsored enterprises |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 1,023,664 | 877,590
Gross Unrealized Gains | 0 | 0
Gross Unrealized Losses | (84,929) | (71,645)
Fair Value | 938,735 | 805,945
Corporate debt securities and other debt securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 8,984 | 8,908
Gross Unrealized Gains | 0 | 0
Gross Unrealized Losses | (336) | (307)
Fair Value | $ 8,648 | $ 8,601

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