Off-Balance Sheet Guarantees and Long Term Standby Purchase Commitments - Off-Balance Sheet Guaranteed Securities (Details) (Variable Interest Entity, Not Primary Beneficiary [Member], USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Off Balance Sheet Farm & Ranch Farmer Mac Guaranteed Securities AgVantage [Member]
Long-term Purchase Commitment [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	$ 970,000	$ 970,000
Off Balance Sheet Farm & Ranch Guaranteed Securities [Member]
Long-term Purchase Commitment [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	801,704	911,370
Off Balance Sheet USDA Guarantees - Farmer Mac Guaranteed Securities [Member]
Long-term Purchase Commitment [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	21,094	29,658
Off Balance Sheet Rural Utilities Farmer Mac Guaranteed Securities AgVantage [Member]
Long-term Purchase Commitment [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	12,667	12,669
Off Balance Sheet Farmer Mac Guaranteed Securities [Member]
Long-term Purchase Commitment [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	$ 1,805,465	$ 1,923,697