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Investment Securities and Equity Securities with Readily Determinable Fair Values (Details) - USD ($) $ in Thousands | Mar. 31, 2019 | Dec. 31, 2018
--- | --- | ---
Held-to-maturity securities |  |
Amortized cost | $ 2,400 | $ 1,200
Estimated fair value | 2,400 | 1,200
Carrying Value | 2,400 | 1,200
Available-for-sale securities |  |
Amortized cost, Available-for-sale securities | 3,447,719 | 3,481,165
Gross Unrealized Gains | 11,935 |
Gross Unrealized Losses | (49,566) |
Available for sale debt securities | 3,410,088 | 3,411,350
Equity Securities | 6,075 | 5,937
Total Amortized cost |  | 3,481,165
Total Gross unrealized gains |  | 9,459
Total Gross unrealized losses |  | 79,274
Assets/liabilities measured at fair value |  |
Available-for-sale securities |  |
Available for sale debt securities | 3,410,088 |
Available for sale debt securities and equity securities |  | 3,411,350
Carrying Value |  |
Available-for-sale securities |  |
Available for sale debt securities | 3,410,088 |
Available for sale debt securities and equity securities |  | 3,411,350
Residential mortgage-backed securities |  |
Available-for-sale securities |  |
Amortized cost, Available-for-sale securities | 3,303,579 | 3,295,366
Gross Unrealized Gains | 9,002 | 6,813
Gross Unrealized Losses | (49,551) | (79,169)
Residential mortgage-backed securities | Assets/liabilities measured at fair value |  |
Available-for-sale securities |  |
Available for sale debt securities | 3,263,030 | 3,223,010
Residential mortgage-backed securities | Carrying Value |  |
Available-for-sale securities |  |
Available for sale debt securities | 3,263,030 | 3,223,010
Mortgage-backed securities by Ginnie Mae |  |
Available-for-sale securities |  |
Available for sale debt securities | 574,588 | 501,293
Mortgage-backed securities by Fannie Mae and Freddie Mac |  |
Available-for-sale securities |  |
Available for sale debt securities | 2,688,442 | 2,721,717
Obligations of states and political subdivisions |  |
Available-for-sale securities |  |
Amortized cost, Available-for-sale securities | 144,140 | 185,799
Gross Unrealized Gains | 2,933 | 2,646
Gross Unrealized Losses | (15) | (105)
Obligations of states and political subdivisions | Assets/liabilities measured at fair value |  |
Available-for-sale securities |  |
Available for sale debt securities | 147,058 | 188,340
Obligations of states and political subdivisions | Carrying Value |  |
Available-for-sale securities |  |
Available for sale debt securities | 147,058 | 188,340
Other securities |  |
Held-to-maturity securities |  |
Amortized cost | 2,400 | 1,200
Estimated fair value | 2,400 | 1,200
Carrying Value | $ 2,400 | $ 1,200

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