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Securities (Schedule of Available-for-sale Securities) (Details) - USD ($) $ in Thousands | Dec. 31, 2019 | Dec. 31, 2018
--- | --- | ---
Debt Securities, Available-for-sale [Line Items] |  |
Total available-for-sale debt securities, Amortized Cost | $ 3,320,648 | $ 2,806,900
Gross Unrealized Gains | 19,805 | 5,714
Gross Unrealized Losses | (23,239) | (70,767)
Available-for-sale debt securities, Fair Value | 3,317,214 | 2,741,847
U.S. Treasury securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Total available-for-sale debt securities, Amortized Cost | 177,215 | 577,561
Gross Unrealized Gains | 0 | 153
Gross Unrealized Losses | (793) | (12,899)
Available-for-sale debt securities, Fair Value | 176,422 | 564,815
U.S. government agency and U.S. government sponsored enterprise debt securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Total available-for-sale debt securities, Amortized Cost | 584,275 | 219,485
Gross Unrealized Gains | 1,377 | 382
Gross Unrealized Losses | (4,407) | (2,694)
Available-for-sale debt securities, Fair Value | 581,245 | 217,173
U.S. government agency and U.S. government sponsored enterprise mortgage-backed securities - Commercial mortgage-backed securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Total available-for-sale debt securities, Amortized Cost | 599,814 | 420,486
Gross Unrealized Gains | 8,551 | 811
Gross Unrealized Losses | (4,894) | (12,694)
Available-for-sale debt securities, Fair Value | 603,471 | 408,603
U.S. government agency and U.S. government sponsored enterprise mortgage-backed securities - Residential mortgage-backed securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Total available-for-sale debt securities, Amortized Cost | 998,447 | 957,219
Gross Unrealized Gains | 6,927 | 4,026
Gross Unrealized Losses | (1,477) | (14,552)
Available-for-sale debt securities, Fair Value | 1,003,897 | 946,693
Municipal securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Total available-for-sale debt securities, Amortized Cost | 101,621 | 82,965
Gross Unrealized Gains | 790 | 87
Gross Unrealized Losses | (109) | (1,032)
Available-for-sale debt securities, Fair Value | 102,302 | 82,020
Non-agency commercial mortgage-backed securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Total available-for-sale debt securities, Amortized Cost | 86,609 | 25,826
Gross Unrealized Gains | 1,947 | 226
Gross Unrealized Losses | (6) | 0
Available-for-sale debt securities, Fair Value | 88,550 | 26,052
Non-agency residential mortgage-backed securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Total available-for-sale debt securities, Amortized Cost | 46,830 | 10,109
Gross Unrealized Gains | 3 | 7
Gross Unrealized Losses | (285) | (185)
Available-for-sale debt securities, Fair Value | 46,548 | 9,931
Corporate debt securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Total available-for-sale debt securities, Amortized Cost | 11,250 | 11,250
Gross Unrealized Gains | 12 | 0
Gross Unrealized Losses | (113) | (381)
Available-for-sale debt securities, Fair Value | 11,149 | 10,869
Foreign bonds |  |
Debt Securities, Available-for-sale [Line Items] |  |
Total available-for-sale debt securities, Amortized Cost | 354,481 | 489,378
Gross Unrealized Gains | 198 | 0
Gross Unrealized Losses | (507) | (26,330)
Available-for-sale debt securities, Fair Value | 354,172 | 463,048
Asset-backed securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Total available-for-sale debt securities, Amortized Cost | 66,106 | 12,621
Gross Unrealized Gains | 0 | 22
Gross Unrealized Losses | (1,354) | 0
Available-for-sale debt securities, Fair Value | 64,752 | $ 12,643
CLOs |  |
Debt Securities, Available-for-sale [Line Items] |  |
Total available-for-sale debt securities, Amortized Cost | 294,000 |
Gross Unrealized Gains | 0 |
Gross Unrealized Losses | (9,294) |
Available-for-sale debt securities, Fair Value | $ 284,706 |

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