Farmer Mac Guaranteed Securities and USDA Guaranteed Securities - Trading Securities (Details) (USDA Securities [Member], USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading, at fair value	$ 37,593	$ 40,310
USDA Guarantees [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading Securities, Debt, Amortized Cost	38,277	41,160
Trading, at fair value	$ 37,593	$ 40,310
Trading Securities, Weighted-Average Yield	5.54%	5.60%