Farmer Mac Guaranteed Securities and USDA Guaranteed Securities - Trading Securities (Details) (USDA Securities [Member], USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading, at fair value	$ 40,310	$ 58,344
USDA Guarantees [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading Securities, Debt, Amortized Cost	41,160	60,345
Trading, at fair value	$ 40,310	$ 58,344
Trading Securities, Weighted-Average Yield	5.60%	5.60%