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Investment Securities Available for Sale (Schedule of Gross Unrealized Losses on Investment Securities and Fair Value) (Details) - USD ($) $ in Thousands | Sep. 30, 2023 | Dec. 31, 2022
--- | --- | ---
Debt Securities, Available-for-sale [Line Items] |  |
Less than 12 months, fair value | $ 856,366 | $ 2,523,310
Less than 12 months, gross unrealized losses | (34,206) | (173,930)
12 months or longer, fair value | 8,355,473 | 6,989,855
12 months or longer, gross unrealized losses | (1,903,358) | (1,423,854)
Total, fair value | 9,211,839 | 9,513,165
Total, gross unrealized losses | (1,937,564) | (1,597,784)
U.S. Treasury securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Less than 12 months, fair value | 38,011 | 139,737
Less than 12 months, gross unrealized losses | (261) | (6,789)
12 months or longer, fair value | 446,097 | 307,582
12 months or longer, gross unrealized losses | (47,070) | (37,351)
Total, fair value | 484,108 | 447,319
Total, gross unrealized losses | (47,331) | (44,140)
U.S. Government agency securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Less than 12 months, fair value | 0 | 28,938
Less than 12 months, gross unrealized losses | 0 | (1,053)
12 months or longer, fair value | 47,506 | 19,603
12 months or longer, gross unrealized losses | (4,634) | (2,560)
Total, fair value | 47,506 | 48,541
Total, gross unrealized losses | (4,634) | (3,613)
Mortgage-backed securities issued by U.S. Government agencies |  |
Debt Securities, Available-for-sale [Line Items] |  |
Less than 12 months, fair value | 350,730 | 187,655
Less than 12 months, gross unrealized losses | (14,758) | (5,952)
12 months or longer, fair value | 541,524 | 521,395
12 months or longer, gross unrealized losses | (133,813) | (107,516)
Total, fair value | 892,254 | 709,050
Total, gross unrealized losses | (148,571) | (113,468)
Mortgage-backed securities issued by U.S. Government sponsored enterprises |  |
Debt Securities, Available-for-sale [Line Items] |  |
Less than 12 months, fair value | 315,190 | 1,473,348
Less than 12 months, gross unrealized losses | (14,825) | (120,135)
12 months or longer, fair value | 5,946,562 | 5,365,233
12 months or longer, gross unrealized losses | (1,505,174) | (1,130,105)
Total, fair value | 6,261,752 | 6,838,581
Total, gross unrealized losses | (1,519,999) | (1,250,240)
Collateralized mortgage obligations issued by U.S. Government agencies or sponsored enterprises |  |
Debt Securities, Available-for-sale [Line Items] |  |
Less than 12 months, fair value | 0 | 119,649
Less than 12 months, gross unrealized losses | 0 | (10,311)
12 months or longer, fair value | 578,836 | 535,478
12 months or longer, gross unrealized losses | (131,764) | (104,060)
Total, fair value | 578,836 | 655,127
Total, gross unrealized losses | (131,764) | (114,371)
Commercial mortgage-backed securities issued by U.S. Government agencies or sponsored enterprises |  |
Debt Securities, Available-for-sale [Line Items] |  |
Less than 12 months, fair value | 152,435 | 565,382
Less than 12 months, gross unrealized losses | (4,362) | (29,383)
12 months or longer, fair value | 786,300 | 240,564
12 months or longer, gross unrealized losses | (80,567) | (42,262)
Total, fair value | 938,735 | 805,946
Total, gross unrealized losses | (84,929) | (71,645)
Corporate debt securities and other debt securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Less than 12 months, fair value | 0 | 8,601
Less than 12 months, gross unrealized losses | 0 | (307)
12 months or longer, fair value | 8,648 | 0
12 months or longer, gross unrealized losses | (336) | 0
Total, fair value | 8,648 | 8,601
Total, gross unrealized losses | $ (336) | $ (307)

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