Farmer Mac Guaranteed Securities and USDA Guaranteed Securities - Farmer Mac Guaranteed Securities and USDA Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Farmer Mac Guaranteed Securities and USDA Securities [Member]
Available-for-sale Securities [Abstract]
Available-for-Sale Securities Unpaid Principal Balance	$ 6,851,259	$ 6,045,828
Available-for-sale Securities, Amortized Cost Basis	6,852,716	6,047,385
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax	125,315	64,131
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	60,223	70,567
Available-for-sale, at fair value	6,917,808	6,040,949
Farmer Mac Guaranteed Securities [Member]
Held-to-Maturity Securities [Abstract]
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	1,153,646
Held-to-maturity Securities, Fair Value	1,165,954
Available-for-sale Securities [Abstract]
Available-for-Sale Securities Unpaid Principal Balance	4,945,802	4,196,506
Available-for-sale Securities, Amortized Cost Basis	4,945,481	4,196,173
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax	52,201	26,971
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	60,201	70,539
Available-for-sale, at fair value	4,937,481	4,152,605
USDA Securities [Member]
Available-for-sale Securities [Abstract]
Available-for-sale, at fair value	1,980,327	1,888,344
Trading Securities [Abstract]
Trading, at fair value	23,489	28,975
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)	1,457	1,557
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)	(321)	(333)
Institutional Credit [Member] \| Farmer Mac Guaranteed Securities [Member]
Held-to-Maturity Securities [Abstract]
Held-to-Maturity Unpaid Principal Balance	1,156,203	1,274,431
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	1,153,646	1,274,016
Held to Maturity; Unrealized Holding Gains	13,203	7,801
Held to Maturity - Unrealized Holding Loss	(895)	0
Held-to-maturity Securities, Fair Value	1,165,954	1,281,817
Available-for-sale Securities [Abstract]
Available-for-Sale Securities Unpaid Principal Balance	4,913,438	4,164,952
Available-for-sale Securities, Amortized Cost Basis	4,913,400	4,164,952
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax	51,458	26,831
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	60,201	70,539
Available-for-sale, at fair value	4,904,657	4,121,244
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)	(2,557)	(415)
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)	(38)	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	32,364	31,554
Available-for-sale Securities, Amortized Cost Basis	32,081	31,221
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax	743	140
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	0	0
Available-for-sale, at fair value	32,824	31,361
USDA Guarantees [Member] \| USDA Securities [Member]
Available-for-sale Securities [Abstract]
Available-for-Sale Securities Unpaid Principal Balance	1,905,457	1,849,322
Available-for-sale Securities, Amortized Cost Basis	1,907,235	1,851,212
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax	73,114	37,160
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax	22	28
Available-for-sale, at fair value	1,980,327	1,888,344
Trading Securities [Abstract]
Trading Securities Unpaid Principal Balance	21,958	27,129
Trading Securities, Debt, Amortized Cost	23,364	29,063
Trading Securities, Unrealized Gains	207	125
Trading Securities, Unrealized Holding Loss	82	213
Trading, at fair value	23,489	28,975
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)	(283)	(333)
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)	1,778	1,890
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)	$ 1,406	$ 1,934

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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 of accumulated unrealized gain on investments in debt securities classified as held-to-maturity.

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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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