Farmer Mac Guaranteed Securities and USDA Guaranteed Securities - Farmer Mac Guaranteed Securities and USDA Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Farmer Mac Guaranteed Securities and USDA Securities [Member]
Available-for-sale Securities [Abstract]
Available-for-Sale Securities Unpaid Principal Balance	$ 6,020,416	$ 5,370,717
Available-for-sale Securities, Amortized Cost Basis	6,022,100	5,373,437
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax	64,410	48,529
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	75,418	31,463
Available-for-sale, at fair value	6,011,092	5,390,503
Farmer Mac Guaranteed Securities [Member]
Held-to-Maturity Securities [Abstract]
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	1,276,153
Held-to-maturity Securities, Fair Value	1,291,290
Available-for-sale Securities [Abstract]
Available-for-Sale Securities Unpaid Principal Balance	4,194,158	3,652,904
Available-for-sale Securities, Amortized Cost Basis	4,193,808	3,652,462
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax	37,929	36,679
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	75,067	29,860
Available-for-sale, at fair value	4,156,670	3,659,281
USDA Securities [Member]
Available-for-sale Securities [Abstract]
Available-for-sale, at fair value	1,854,422	1,731,222
Trading Securities [Abstract]
Trading, at fair value	31,936	40,310
Available-for-sale Securities [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)	1,684	2,720
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)	(350)	(442)
Institutional Credit [Member] \| Farmer Mac Guaranteed Securities [Member]
Held-to-Maturity Securities [Abstract]
Held-to-Maturity Unpaid Principal Balance	1,275,549	1,785,340
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	1,276,153	1,794,620
Held to Maturity; Unrealized Holding Gains	15,137	6,211
Held to Maturity - Unrealized Holding Loss	0	(255)
Held-to-maturity Securities, Fair Value	1,291,290	1,800,576
Available-for-sale Securities [Abstract]
Available-for-Sale Securities Unpaid Principal Balance	4,162,940	3,625,073
Available-for-sale Securities, Amortized Cost Basis	4,162,940	3,625,073
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax	37,899	36,442
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	74,877	29,853
Available-for-sale, at fair value	4,125,962	3,631,662
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)	604	9,280
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)	0	0
USDA Guarantees [Member]
Schedule of Held-to-Maturity, Available-for-sale, and Trading Securities [Line Items]
Unamortized Premium/(Discount)	500	200
USDA Guarantees [Member] \| Farmer Mac Guaranteed Securities [Member]
Available-for-sale Securities [Abstract]
Available-for-Sale Securities Unpaid Principal Balance	31,218	27,831
Available-for-sale Securities, Amortized Cost Basis	30,868	27,389
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax	30	237
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	190	7
Available-for-sale, at fair value	30,708	27,619
USDA Guarantees [Member] \| USDA Securities [Member]
Available-for-sale Securities [Abstract]
Available-for-Sale Securities Unpaid Principal Balance	1,826,258	1,717,813
Available-for-sale Securities, Amortized Cost Basis	1,828,292	1,720,975
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax	26,481	11,850
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	351	1,603
Available-for-sale, at fair value	1,854,422	1,731,222
Trading Securities [Abstract]
Trading Securities Unpaid Principal Balance	30,437	38,412
Trading Securities, Debt, Amortized Cost	32,666	41,160
Trading Securities, Unrealized Gains	82	114
Trading Securities, Unrealized Holding Loss	812	964
Trading, at fair value	31,936	40,310
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)	(350)	(442)
USDA Guarantees [Member] \| Available-for-sale Securities [Member] \| USDA Securities [Member]
Schedule of Held-to-Maturity, Available-for-sale, and Trading Securities [Line Items]
Unamortized Premium/(Discount)	2,034	3,162
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)	$ 2,229	$ 2,748

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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt securities classified as available-for-sale.

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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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The amount of debt discount (net of debt premium) that was originally recognized at the issuance of the instrument that has yet to be amortized.

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Amount before other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity.

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