Equity - Non-controlling interest (Details) (Farmer Mac II LLC [Member], USD $) In Millions, except Share data, unless otherwise specified	0 Months Ended			3 Months Ended
	Jan. 25, 2010 Private Placement [Member]	Jan. 25, 2010 Private Placement [Member] Preferred Stock [Member]	Mar. 31, 2014 Private Placement [Member] Preferred Stock [Member]	Mar. 31, 2014 March 30, 2015 To But Excluding March 30, 2020 [Member] Preferred Stock [Member]	Mar. 31, 2014 Issuance To But Excluding March 30, 2015 [Member] Preferred Stock [Member]	Mar. 31, 2014 March 30, 2020 and Thereafter [Member] Preferred Stock [Member]
Class of Stock [Line Items]
Sale of Stock, Consideration Received on Transaction	$ 250.0
Sale of Stock, Number of Shares Issued in Transaction		250,000
Preferred Stock, Liquidation Preference Per Share			$ 1,000
Preferred Stock, Dividend Rate, Percentage				10.875%	8.875%
Preferred Stock, Dividend Variable Rate, Percentage						8.211%