Off-Balance Sheet Guarantees and Long Term Standby Purchase Commitments - Narrative (Details) (USD $)	3 Months Ended	6 Months Ended								6 Months Ended
	Jun. 30, 2012	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012 Collateralized Loan Obligations LTSPCs	Dec. 31, 2011 Collateralized Loan Obligations LTSPCs	Jun. 30, 2012 Collateralized Loan Obligations LTSPCs On Or After January 1, 2003	Dec. 31, 2011 Collateralized Loan Obligations LTSPCs On Or After January 1, 2003	Jun. 30, 2012 Collateralized Loan Obligations Variable Interest Entity, Not Primary Beneficiary Financial Guarantee	Dec. 31, 2011 Collateralized Loan Obligations Variable Interest Entity, Not Primary Beneficiary Financial Guarantee	Jun. 30, 2012 Collateralized Loan Obligations Variable Interest Entity, Not Primary Beneficiary LTSPCs	Jun. 30, 2012 Farmer Mac Guaranteed Securities Collateralized Loan Obligations Variable Interest Entity, Not Primary Beneficiary Financial Guarantee	Jun. 30, 2012 Farmer Mac Guaranteed Securities AgVantage Collateralized Loan Obligations Variable Interest Entity, Not Primary Beneficiary Financial Guarantee
Guarantor Obligations [Line Items]
Guarantor carrying value						$ 16,800,000	$ 15,100,000	$ 17,300,000	$ 12,300,000
Deconsolidation of loans held for investment in consolidated trusts and debt securities of consolidated trusts held by third parties - transferred to off-balance sheet Farmer Mac I Guaranteed Securities	460,300,000	460,261,000	0
Deconsolidiation, Increase to guarantee and commitment obligations								5,900,000
Securitization interests continued to be held by transferor, weighted average remaining maturity										13 years 2 months 11 days	13 years 8 months 11 days	4 years 9 months 17 days
Maximum principal amount of potential undiscounted future payments				$ 1,900,000,000	$ 1,800,000,000