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Securities (Details) - USD ($) $ in Thousands | Sep. 30, 2017 | Dec. 31, 2016
--- | --- | ---
Schedule of Available-for-sale Securities |  |
Amortized Cost | $ 2,992,763 | $ 3,385,441
Gross Unrealized Gains | 6,350 | 6,695
Gross Unrealized Losses | (42,337) | (56,341)
Fair Value | 2,956,776 | 3,335,795
Schedule of Held-to-maturity Security |  |
Amortized Cost | 0 | 143,971
Fair Value |  | 144,593
Carrying amount of investment security held-to-maturity transferred to available-for-sale | 115,600 |
Investment Securities |  |
Amortized Cost | 2,992,763 | 3,529,412
Gross Unrealized Gains | 6,350 | 7,317
Gross Unrealized Losses | (42,337) | (56,341)
Fair Value | 2,956,776 | 3,480,388
U.S. Treasury securities |  |
Schedule of Available-for-sale Securities |  |
Amortized Cost | 533,035 | 730,287
Gross Unrealized Gains | 0 | 21
Gross Unrealized Losses | (6,703) | (9,829)
Fair Value | 526,332 | 720,479
U.S. government agency and U.S. government sponsored enterprise debt securities |  |
Schedule of Available-for-sale Securities |  |
Amortized Cost | 191,727 | 277,891
Gross Unrealized Gains | 81 | 224
Gross Unrealized Losses | (2,623) | (3,249)
Fair Value | 189,185 | 274,866
U.S. government agency and U.S. government sponsored enterprise mortgage-backed securities - Commercial mortgage-backed securities |  |
Schedule of Available-for-sale Securities |  |
Amortized Cost | 321,943 | 272,672
Gross Unrealized Gains | 326 | 345
Gross Unrealized Losses | (7,097) | (6,218)
Fair Value | 315,172 | 266,799
U.S. government agency and U.S. government sponsored enterprise mortgage-backed securities - Residential mortgage-backed securities |  |
Schedule of Available-for-sale Securities |  |
Amortized Cost | 1,154,026 | 1,266,372
Gross Unrealized Gains | 4,790 | 3,924
Gross Unrealized Losses | (7,882) | (11,549)
Fair Value | 1,150,934 | 1,258,747
Municipal securities |  |
Schedule of Available-for-sale Securities |  |
Amortized Cost | 116,798 | 148,302
Gross Unrealized Gains | 900 | 1,252
Gross Unrealized Losses | (456) | (1,900)
Fair Value | 117,242 | 147,654
Non-agency residential mortgage-backed securities | Investment grade |  |
Schedule of Available-for-sale Securities |  |
Amortized Cost | 9,680 | 11,592
Gross Unrealized Gains | 21 | 0
Gross Unrealized Losses | (7) | (115)
Fair Value | 9,694 | 11,477
Corporate debt securities | Investment grade |  |
Schedule of Available-for-sale Securities |  |
Amortized Cost | 2,464 | 222,190
Gross Unrealized Gains | 0 | 562
Gross Unrealized Losses | (137) | (375)
Fair Value | 2,327 | 222,377
Corporate debt securities | Non-investment grade |  |
Schedule of Available-for-sale Securities |  |
Amortized Cost | 10,191 | 10,191
Gross Unrealized Gains | 0 | 0
Gross Unrealized Losses | (576) | (1,018)
Fair Value | 9,615 | 9,173
Foreign bonds | Investment grade |  |
Schedule of Available-for-sale Securities |  |
Amortized Cost | 505,395 | 405,443
Gross Unrealized Gains | 229 | 30
Gross Unrealized Losses | (16,484) | (21,579)
Fair Value | 489,140 | 383,894
Foreign bonds | Investment grade | Multilateral development bank |  |
Schedule of Available-for-sale Securities |  |
Fair Value | 458,900 | 353,600
Other securities |  |
Schedule of Available-for-sale Securities |  |
Amortized Cost | 147,504 | 40,501
Gross Unrealized Gains | 3 | 337
Gross Unrealized Losses | (372) | (509)
Fair Value | 147,135 | 40,329
Non-agency commercial mortgage-backed security |  |
Schedule of Held-to-maturity Security |  |
Amortized Cost | 0 | 143,971
Gross Unrealized Gains | 0 | 622
Gross Unrealized Losses | 0 | 0
Fair Value | $ 0 | $ 144,593

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