Equity - Non-controlling interest (Details) (USD $)	0 Months Ended	12 Months Ended
	Jan. 25, 2010	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Farmer Mac II LLC [Member]
Class of Stock [Line Items]
Sale of Stock, Consideration Received on Transaction	$ 250,000,000
Farmer Mac II LLC [Member] | Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock, Liquidation Preference Per Share		1,000
Farmer Mac II LLC [Member] | Private Placement [Member] | Preferred Stock [Member]
Class of Stock [Line Items]
Sale of Stock, Number of Shares Issued in Transaction	250,000
Farmer Mac II LLC [Member] | March 30, 2015 To But Excluding March 30, 2020 [Member] | Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock, Dividend Rate, Percentage		10.875%
Farmer Mac II LLC [Member] | Issuance To But Excluding March 30, 2015 [Member] | Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock, Dividend Rate, Percentage		8.875%
Farmer Mac II LLC [Member] | March 30, 2020 and Thereafter [Member] | Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock, Dividend Variable Rate, Percentage		8.211%
Non-controlling Interest - Preferred Stock [Member]
Class of Stock [Line Items]
Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests		6,000,000	$ 0	$ 0