Farmer Mac Guaranteed Securities and USDA Guaranteed Securities - Narrative (Details) (USD $)							0 Months Ended
	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2013 Farmer Mac Guarantee	Mar. 31, 2012 Farmer Mac Guarantee	Jun. 30, 2013 Farm & Ranch Guaranteed Securities [Member] Farmer Mac Guarantee position	Dec. 31, 2012 Farm & Ranch Guaranteed Securities [Member] Farmer Mac Guarantee	Jun. 30, 2013	Dec. 31, 2012	Mar. 31, 2013	Jun. 30, 2013 Payment Guarantee [Member]	Dec. 31, 2012 Payment Guarantee [Member]	Jun. 30, 2013 Farmer Mac Guarantee	Dec. 31, 2012 Farmer Mac Guarantee	Jun. 30, 2013 Farmer Mac Guaranteed Securities - Rural Utilities Farmer Mac Guarantee	Dec. 31, 2012 Farmer Mac Guaranteed Securities - Rural Utilities Farmer Mac Guarantee	Jun. 30, 2013 Categories of Investments, Marketable Securities, Trading Securities [Member] Payment Guarantee [Member]	Dec. 31, 2012 Categories of Investments, Marketable Securities, Trading 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] Farm & Ranch Guaranteed Securities [Member] Farmer Mac Guarantee	Dec. 31, 2012 Available-for-sale Securities [Member] Farm & Ranch Guaranteed Securities [Member] Farmer Mac Guarantee	Jun. 30, 2013 Available-for-sale Securities [Member]	Dec. 31, 2012 Available-for-sale Securities [Member]	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	Dec. 31, 2012 Available-for-sale Securities [Member] Farmer Mac Guarantee	Jun. 30, 2013 Available-for-sale Securities [Member] Farmer Mac Guaranteed Securities - Rural Utilities Farmer Mac Guarantee	Dec. 31, 2012 Available-for-sale Securities [Member] Farmer Mac Guaranteed Securities - Rural Utilities Farmer Mac Guarantee
Schedule of Available-for-sale and Trading Securities [Line Items]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of securities in unrealized loss position greater than twelve months					9
Available-for-sale Securities			$ 5,003,610,000	$ 4,663,944,000	$ 3,438,000,000	$ 3,339,200,000	$ 1,549,502,000	$ 1,461,184,000		$ 6,553,112,000	$ 6,125,128,000	$ 25,339,000	$ 26,238,000	$ 1,540,271,000	$ 1,298,506,000
Available-for-sale Securities, Unrealized Losses			(31,635,000)	(9,056,000)	(14,567,000)	(5,094,000)	(16,084,000)	(169,000)		(47,719,000)	(9,225,000)	0	(14,000)	(17,068,000)	(3,948,000)
Available-for-sale Securities, Fair Value Disclosure			5,058,853,000	4,766,258,000	3,498,474,000	3,426,489,000	1,543,764,000	1,486,595,000		6,602,617,000	6,252,853,000	25,794,000	26,681,000	1,534,585,000	1,313,088,000
Available-for-sale Securities, Amortized Cost Basis			5,003,301,000	4,663,652,000	3,438,143,000	3,339,360,000	1,554,676,000	1,467,159,000		6,557,977,000	6,130,811,000	24,887,000	25,786,000	1,540,271,000	1,298,506,000
Trading Securities Unpaid Principal Balance							69,358,000	98,499,000
Available-for-sale Securities, Unrealized Gains			87,187,000	111,662,000	74,898,000	92,223,000	5,172,000	19,605,000		92,359,000	131,267,000	907,000	909,000	11,382,000	18,530,000
Debt Instrument, Unamortized Discount (Premium), Net																10,260,000	12,098,000	(309,000)	(292,000)	143,000	160,000	5,174,000	5,975,000	4,865,000	5,683,000	(452,000)	(452,000)	0	0
Trading Securities Amortized Cost							74,753,000	104,914,000
Trading Securities, Unrealized Holding Gain							438,000	624,000
Trading securities							73,592,000	104,188,000
Trading securities weighted-average yield								5.77%	5.69%
Trading Securities, Unrealized Holding Loss							1,599,000	1,350,000
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
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses	$ 15,792,000	$ 23,521,000			$ 2,700,000