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Securities - Amortized Cost and Fair Value (Details) $ in Thousands | 6 Months Ended |
--- | --- | ---
Jun. 30, 2017 USD ($) | Jun. 30, 2016 USD ($) | Dec. 31, 2016 USD ($)
Securities Available-for-Sale |  |  |
Amortized Cost | $ 571,208 |  | $ 545,433
Gross Unrealized Gains | 5,557 |  | 1,011
Gross Unrealized Losses | (8,538) |  | (14,606)
Fair Value | 568,227 |  | 531,838
Other disclosures |  |  |
Purchases | 205,755 | $ 122,700 |
Sales | 100,856 | $ 44,993 |
U.S. government agencies |  |  |
Securities Available-for-Sale |  |  |
Amortized Cost |  |  | 42,511
Gross Unrealized Losses |  |  | (977)
Fair Value |  |  | 41,534
States and political subdivisions |  |  |
Securities Available-for-Sale |  |  |
Amortized Cost | 222,098 |  | 68,718
Gross Unrealized Gains | 4,472 |  | 258
Gross Unrealized Losses | (1,052) |  | (273)
Fair Value | 225,518 |  | 68,703
Corporate bonds |  |  |
Securities Available-for-Sale |  |  |
Amortized Cost | 12,807 |  | 10,957
Gross Unrealized Gains | 58 |  | 9
Gross Unrealized Losses | (249) |  | (336)
Fair Value | 12,616 |  | 10,630
Collateralized mortgage obligations |  |  |
Securities Available-for-Sale |  |  |
Amortized Cost | 102,717 |  | 174,352
Gross Unrealized Gains | 159 |  | 374
Gross Unrealized Losses | (1,963) |  | (3,799)
Fair Value | 100,913 |  | 170,927
Asset-backed securities |  |  |
Securities Available-for-Sale |  |  |
Amortized Cost | 144,812 |  | 146,391
Gross Unrealized Gains | 557 |  | 341
Gross Unrealized Losses | (4,984) |  | (8,325)
Fair Value | 140,385 |  | 138,407
FFEL |  |  |
Other disclosures |  |  |
Asset-backed securities | $ 119,300 |  |
Percentage of outstanding principal amount of loans guaranteed by US Department of Education | 97.00 |  |
Total added credit enhancement in the form of overcollaterization and/or subordination of outstanding principal | $ 13,400 |  |
Percentage of total added credit enhancement in the form of overcollaterization and/or subordination of outstanding principal | 10.43 |  |
Collateralized loan obligations |  |  |
Securities Available-for-Sale |  |  |
Amortized Cost | $ 67,735 |  | 102,504
Gross Unrealized Gains | 305 |  | 29
Gross Unrealized Losses | (91) |  | (896)
Fair Value | 67,949 |  | $ 101,637
U.S. government agency mortgage-backed |  |  |
Securities Available-for-Sale |  |  |
Amortized Cost | 21,039 |  |
Gross Unrealized Gains | 6 |  |
Gross Unrealized Losses | (199) |  |
Fair Value | 20,846 |  |
GCO Education Loan Funding Corp |  |  |
Other disclosures |  |  |
Additions to total securities portfolio | 27,500 |  |
Securities pledged to secure deposits and for other purposes | $ 26,000 |  |

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