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Securities - Asset-backed Securities (Details) - USD ($) $ in Thousands | 12 Months Ended |
--- | --- | ---
Dec. 31, 2015 | Dec. 31, 2014
Asset-backed securities |  |
Amortized Cost | $ 470,719 | $ 391,694
Fair Value | $ 456,066 | 385,486
Asset-backed securities |  |
Asset-backed securities |  |
Percentage of original principal amount of the loans made under FFEL which is guaranteed by the U.S. Department of Education | 97.00% |
Amortized Cost | $ 241,872 | 175,565
Fair Value | 231,908 | $ 173,496
Credit Concentration Risk | Stockholders' Equity | Access Group | Asset-backed securities |  |
Asset-backed securities |  |
Amortized Cost | 73,293 |
Fair Value | 70,254 |
Credit Concentration Risk | Stockholders' Equity | Northstar Education Finance | Asset-backed securities |  |
Asset-backed securities |  |
Amortized Cost | 23,359 |
Fair Value | 23,291 |
Credit Concentration Risk | Stockholders' Equity | GCO Education Loan Funding Corp | Asset-backed securities |  |
Asset-backed securities |  |
Amortized Cost | 37,508 |
Fair Value | $ 35,263 |
Minimum | Credit Concentration Risk | Stockholders' Equity | Access Group | Asset-backed securities |  |
Asset-backed securities |  |
Credit risk as a percentage of benchmark | 10.00% |
Minimum | Credit Concentration Risk | Stockholders' Equity | Northstar Education Finance | Asset-backed securities |  |
Asset-backed securities |  |
Credit risk as a percentage of benchmark | 10.00% |
Minimum | Credit Concentration Risk | Stockholders' Equity | GCO Education Loan Funding Corp | Asset-backed securities |  |
Asset-backed securities |  |
Credit risk as a percentage of benchmark | 10.00% |

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