Farmer Mac Guaranteed Securities and USDA Guaranteed Securities (Details) (USD $)													0 Months Ended
	Jun. 30, 2013 Payment Guarantee [Member]	Dec. 31, 2012 Payment Guarantee [Member]	Jun. 30, 2013 Payment Guarantee [Member] Categories of Investments, Marketable Securities, Trading Securities [Member]	Dec. 31, 2012 Payment Guarantee [Member] Categories of Investments, Marketable Securities, Trading Securities [Member]	Jun. 30, 2013 Farmer Mac Guarantee	Mar. 31, 2012 Farmer Mac Guarantee	Jun. 30, 2013 Farmer Mac Guarantee Farm & Ranch Guaranteed Securities [Member]	Dec. 31, 2012 Farmer Mac Guarantee Farm & Ranch Guaranteed Securities [Member]	Jun. 30, 2013 Farmer Mac Guarantee	Dec. 31, 2012 Farmer Mac Guarantee	Jun. 30, 2013 Farmer Mac Guarantee Farmer Mac Guaranteed Securities - Rural Utilities	Dec. 31, 2012 Farmer Mac Guarantee Farmer Mac Guaranteed Securities - Rural Utilities	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2013 Available-for-sale Securities [Member] Payment Guarantee [Member]	Dec. 31, 2012 Available-for-sale Securities [Member] Payment Guarantee [Member]	Jun. 30, 2013 Available-for-sale Securities [Member] Farmer Mac Guarantee	Mar. 31, 2012 Available-for-sale Securities [Member] Farmer Mac Guarantee	Jun. 30, 2013 Available-for-sale Securities [Member] Farmer Mac Guarantee Farm & Ranch Guaranteed Securities [Member]	Dec. 31, 2012 Available-for-sale Securities [Member] Farmer Mac Guarantee Farm & Ranch Guaranteed Securities [Member]	Jun. 30, 2013 Available-for-sale Securities [Member] Farmer Mac Guarantee	Dec. 31, 2012 Available-for-sale Securities [Member] Farmer Mac Guarantee	Jun. 30, 2013 Available-for-sale Securities [Member] Farmer Mac Guarantee Farmer Mac Guaranteed Securities - Rural Utilities	Dec. 31, 2012 Available-for-sale Securities [Member] Farmer Mac Guarantee Farmer Mac Guaranteed Securities - Rural Utilities	Jun. 30, 2013 Available-for-sale Securities [Member]	Dec. 31, 2012 Available-for-sale Securities [Member]	Jun. 30, 2013 Trading Account Assets [Member]	Dec. 31, 2012 Trading Account Assets [Member]
Schedule of Available-for-sale and Trading Securities [Line Items]
Available-for-sale, at fair value	$ 6,553,112,000	$ 6,125,128,000			$ 5,003,610,000	$ 4,663,944,000	$ 3,438,000,000	$ 3,339,200,000	$ 25,339,000	$ 26,238,000	$ 1,540,271,000	$ 1,298,506,000	$ 1,549,502,000	$ 1,461,184,000
Debt Instrument, Unamortized Discount (Premium), Net			10,260,000	12,098,000											4,865,000	5,683,000	(309,000)	(292,000)	143,000	160,000	(452,000)	(452,000)	0	0	5,174,000	5,975,000	5,395,000	6,415,000
Available-for-sale Securities, Amortized Cost Basis	6,557,977,000	6,130,811,000			5,003,301,000	4,663,652,000	3,438,143,000	3,339,360,000	24,887,000	25,786,000	1,540,271,000	1,298,506,000	1,554,676,000	1,467,159,000
Available-for-sale Securities, Unrealized Gains	92,359,000	131,267,000			87,187,000	111,662,000	74,898,000	92,223,000	907,000	909,000	11,382,000	18,530,000	5,172,000	19,605,000
Available-for-sale Securities, Unrealized Losses	(47,719,000)	(9,225,000)			(31,635,000)	(9,056,000)	(14,567,000)	(5,094,000)	0	(14,000)	(17,068,000)	(3,948,000)	(16,084,000)	(169,000)
Available-for-sale securities	6,602,617,000	6,252,853,000			5,058,853,000	4,766,258,000	3,498,474,000	3,426,489,000	25,794,000	26,681,000	1,534,585,000	1,313,088,000	1,543,764,000	1,486,595,000
Trading Securities Unpaid Principal Balance													69,358,000	98,499,000
Trading Securities Amortized Cost													74,753,000	104,914,000
Trading Securities, Unrealized Gains													438,000	624,000
Trading Securities, Unrealized Losses													(1,599,000)	(1,350,000)
Trading securities													73,592,000	104,188,000
Marketable Securities	6,622,470,000	6,223,627,000
Marketable Securities, Amortized Cost	6,632,730,000	6,235,725,000
Marketable Securities, Unrealized Gains	92,797,000	131,891,000
Marketable Securities, Unrealized Losses	(49,318,000)	(10,575,000)
Marketable Securities	$ 6,676,209,000	$ 6,357,041,000