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Farmer Mac Guaranteed Securities and USDA Guaranteed Securities - Farmer Mac Guaranteed Securities and USDA Securities (Details) $ in Thousands |  |  | 12 Months Ended |
--- | --- | --- | --- | ---
Dec. 31, 2017 USD ($) position | Dec. 31, 2016 USD ($) position | Dec. 31, 2017 USD ($) position | Dec. 31, 2016 USD ($) position | Dec. 31, 2015 USD ($) | Oct. 01, 2016 USD ($)
Schedule of Held-to-Maturity, Available-for-sale, and Trading Securities [Line Items] |  |  |  |  |  |
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | position | 91 | 97 | 91 | 97 |  |
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | $ 2,106 | $ 7,633 | $ 2,106 | $ 7,633 |  |
Transfer of USDA Guaranteed Securities- Available-for-sale to Held-to-maturity; Unrealized holding gains |  |  |  |  |  | $ 73,100
Trading Securities [Abstract] |  |  |  |  |  |
Transfer of Farmer Mac Guaranteed Securities - Available-for-sale to Held-to-maturity; Unrealized holding gains |  |  |  |  |  | 700
Transfer of Farmer Mac Guaranteed Securities and USDA Guaranteed Securities - Available-for-sale to Held-to-maturity; Unrealized holding gains |  |  |  |  |  | $ 73,800
Farmer Mac Guaranteed Securities and USDA Securities [Member] |  |  |  |  |  |
Schedule of Held-to-Maturity, Available-for-sale, and Trading Securities [Line Items] |  |  |  |  |  |
Unamortized Premium/(Discount) | 62,340 |  | 62,340 |  |  |
Held-to-Maturity Securities [Abstract] |  |  |  |  |  |
Held-to-Maturity Unpaid Principal Balance | 4,181,784 | 3,086,504 | 4,181,784 | 3,086,504 |  |
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment | 4,244,124 | 3,158,456 | 4,244,124 | 3,158,456 |  |
Held to Maturity; Unrealized Holding Gains | 2,119 | 7,192 | 2,119 | 7,192 |  |
Held to Maturity - Unrealized Holding Loss | (66,471) | (99,004) | (66,471) | (99,004) |  |
Held-to-maturity Securities, Fair Value | 4,179,772 | 3,066,644 | 4,179,772 | 3,066,644 |  |
Available-for-sale Securities [Abstract] |  |  |  |  |  |
Available-for-sale Securities, Amortized Cost Basis | 5,496,387 |  | 5,496,387 |  |  |
Available-for-sale, at fair value | 5,471,914 |  | 5,471,914 |  |  |
Farmer Mac Guaranteed Securities [Member] |  |  |  |  |  |
Schedule of Held-to-Maturity, Available-for-sale, and Trading Securities [Line Items] |  |  |  |  |  |
Unamortized Premium/(Discount) | (460) | (1,833) | (460) | (1,833) |  |
Held-to-Maturity Securities [Abstract] |  |  |  |  |  |
Held-to-Maturity Unpaid Principal Balance | 2,126,734 | 1,151,064 | 2,126,734 | 1,151,064 |  |
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment | 2,126,274 | 1,149,231 | 2,126,274 | 1,149,231 |  |
Held to Maturity; Unrealized Holding Gains | 2,119 | 7,192 | 2,119 | 7,192 |  |
Held to Maturity - Unrealized Holding Loss | (11,502) | (3,414) | (11,502) | (3,414) |  |
Held-to-maturity Securities, Fair Value | 2,116,891 | 1,153,009 | 2,116,891 | 1,153,009 |  |
USDA Securities [Member] |  |  |  |  |  |
Trading Securities [Abstract] |  |  |  |  |  |
Trading, at fair value | $ 13,515 | 20,388 | $ 13,515 | 20,388 |  |
Institutional Credit [Member] | Farmer Mac Guaranteed Securities and USDA Securities [Member] |  |  |  |  |  |
Schedule of Held-to-Maturity, Available-for-sale, and Trading Securities [Line Items] |  |  |  |  |  |
Unamortized Premium/(Discount) |  | $ 71,952 |  | $ 71,952 |  |
Institutional Credit [Member] | Farmer Mac Guaranteed Securities [Member] |  |  |  |  |  |
Schedule of Held-to-Maturity, Available-for-sale, and Trading Securities [Line Items] |  |  |  |  |  |
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | position | 36 | 22 | 36 | 22 |  |
Held-to-maturity, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | position | 23 | 7 | 23 | 7 |  |
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year | position | 16 | 10 | 16 | 10 |  |
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss | $ 37,492 | $ 45,452 | $ 37,492 | $ 45,452 |  |
Held-to-Maturity Securities [Abstract] |  |  |  |  |  |
Held-to-Maturity Unpaid Principal Balance | 2,096,754 | 1,115,465 | 2,096,754 | 1,115,465 |  |
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment | 2,095,975 | 1,113,189 | 2,095,975 | 1,113,189 |  |
Held to Maturity; Unrealized Holding Gains | 2,011 | 7,187 | 2,011 | 7,187 |  |
Held to Maturity - Unrealized Holding Loss | (11,429) | (3,175) | (11,429) | (3,175) |  |
Held-to-maturity Securities, Fair Value | 2,086,557 | 1,117,201 | 2,086,557 | 1,117,201 |  |
Available-for-sale Securities [Abstract] |  |  |  |  |  |
Available-for-Sale Securities Unpaid Principal Balance | 5,496,569 | 4,889,007 | 5,496,569 | 4,889,007 |  |
Available-for-sale Securities, Amortized Cost Basis | 5,496,387 | 4,888,904 | 5,496,387 | 4,888,904 |  |
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax | 21,838 | 28,715 | 21,838 | 28,715 |  |
Available-for-sale Securities, Unrealized Losses | (46,311) | (63,934) | (46,311) | (63,934) |  |
Available-for-sale, at fair value | 5,471,914 | 4,853,685 | 5,471,914 | 4,853,685 |  |
Institutional Credit [Member] | Held-to-maturity Securities [Member] | Farmer Mac Guaranteed Securities [Member] |  |  |  |  |  |
Schedule of Held-to-Maturity, Available-for-sale, and Trading Securities [Line Items] |  |  |  |  |  |
Unamortized Premium/(Discount) | (779) | (2,276) | (779) | (2,276) |  |
Institutional Credit [Member] | Available-for-sale Securities [Member] | Farmer Mac Guaranteed Securities [Member] |  |  |  |  |  |
Schedule of Held-to-Maturity, Available-for-sale, and Trading Securities [Line Items] |  |  |  |  |  |
Unamortized Premium/(Discount) | (182) | (103) | (182) | (103) |  |
USDA Guarantees [Member] |  |  |  |  |  |
Schedule of Held-to-Maturity, Available-for-sale, and Trading Securities [Line Items] |  |  |  |  |  |
Unamortized Premium/(Discount) | 300 | 400 | 300 | 400 |  |
USDA Guarantees [Member] | Farmer Mac Guaranteed Securities [Member] |  |  |  |  |  |
Held-to-Maturity Securities [Abstract] |  |  |  |  |  |
Held-to-Maturity Unpaid Principal Balance | 29,980 | 35,599 | 29,980 | 35,599 |  |
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment | 30,299 | 36,042 | 30,299 | 36,042 |  |
Held to Maturity; Unrealized Holding Gains | 108 | 5 | 108 | 5 |  |
Held to Maturity - Unrealized Holding Loss | (73) | (239) | (73) | (239) |  |
Held-to-maturity Securities, Fair Value | 30,334 | 35,808 | 30,334 | 35,808 |  |
USDA Guarantees [Member] | USDA Securities [Member] |  |  |  |  |  |
Schedule of Held-to-Maturity, Available-for-sale, and Trading Securities [Line Items] |  |  |  |  |  |
Unamortized Premium/(Discount) | 62,800 | 73,785 | 62,800 | 73,785 |  |
Held-to-Maturity Securities [Abstract] |  |  |  |  |  |
Held-to-Maturity Unpaid Principal Balance | 2,055,050 | 1,935,440 | 2,055,050 | 1,935,440 |  |
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment | 2,117,850 | 2,009,225 | 2,117,850 | 2,009,225 |  |
Held to Maturity; Unrealized Holding Gains | 0 | 0 | 0 | 0 |  |
Held to Maturity - Unrealized Holding Loss | (54,969) | (95,590) | (54,969) | (95,590) |  |
Held-to-maturity Securities, Fair Value | 2,062,881 | 1,913,635 | 2,062,881 | 1,913,635 |  |
Trading Securities [Abstract] |  |  |  |  |  |
Trading Securities Unpaid Principal Balance | 12,966 | 19,360 | 12,966 | 19,360 |  |
Trading Securities, Debt, Amortized Cost | 13,888 | 20,737 | 13,888 | 20,737 |  |
Trading Securities, Unrealized Gains | 28 | 41 |  |  |  |
Trading Securities, Unrealized Holding Loss | (401) | (390) |  |  |  |
Trading, at fair value | $ 13,515 | $ 20,388 | $ 13,515 | $ 20,388 |  |
Trading Securities, Weighted-Average Yield | 5.33% | 5.44% | 5.33% | 5.44% |  |
USDA Guarantees [Member] | Available-for-sale Securities [Member] | Farmer Mac Guaranteed Securities [Member] |  |  |  |  |  |
Schedule of Held-to-Maturity, Available-for-sale, and Trading Securities [Line Items] |  |  |  |  |  |
Unamortized Premium/(Discount) | $ 319 | $ 443 | $ 319 | $ 443 |  |
USDA Guarantees [Member] | Trading Securities [Member] | USDA Securities [Member] |  |  |  |  |  |
Schedule of Held-to-Maturity, Available-for-sale, and Trading Securities [Line Items] |  |  |  |  |  |
Unamortized Premium/(Discount) | $ 922 | $ 1,377 | 922 | 1,377 |  |
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] |  |  |  |  |  |
Schedule of Held-to-Maturity, Available-for-sale, and Trading Securities [Line Items] |  |  |  |  |  |
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3 |  |  |  | 2,013,151 |  |
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Farmer Mac Guaranteed Securities [Member] | Available-for-sale Securities [Member] |  |  |  |  |  |
Schedule of Held-to-Maturity, Available-for-sale, and Trading Securities [Line Items] |  |  |  |  |  |
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3 |  |  | $ 0 | 32,824 | $ 0 |
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Farmer Mac Guaranteed Securities [Member] | USDA Guarantee [Member] | Available-for-sale Securities [Member] |  |  |  |  |  |
Schedule of Held-to-Maturity, Available-for-sale, and Trading Securities [Line Items] |  |  |  |  |  |
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3 |  |  |  | 2,000,000 |  |
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Farmer Mac Guaranteed Securities [Member] | Farmer Mac Guaranteed Securities [Member] | Available-for-sale Securities [Member] |  |  |  |  |  |
Schedule of Held-to-Maturity, Available-for-sale, and Trading Securities [Line Items] |  |  |  |  |  |
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3 |  |  |  | 32,800 |  |
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Farmer Mac Guaranteed Securities [Member] | Institutional Credit [Member] | Available-for-sale Securities [Member] |  |  |  |  |  |
Schedule of Held-to-Maturity, Available-for-sale, and Trading Securities [Line Items] |  |  |  |  |  |
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3 |  |  |  | 0 |  |
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Farmer Mac Guaranteed Securities [Member] | USDA Guarantees [Member] | Available-for-sale Securities [Member] |  |  |  |  |  |
Schedule of Held-to-Maturity, Available-for-sale, and Trading Securities [Line Items] |  |  |  |  |  |
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3 |  |  |  | $ 32,824 |  |

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