Off-Balance Sheet Guarantees and Long Term Standby Purchase Commitments - Cash Flows From Securitizations (Details) (USD $)	3 Months Ended	12 Months Ended
	Jun. 30, 2012	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Guarantor Obligations [Line Items]
Deconsolidation of guaranteed securities from Loans Held for Investment in consolidated trusts and debt securities of consolidated trusts held by third parties to off-balance sheet	$ 460,300,000	$ 460,261,000	$ 0	$ 414,462,000
Farmer Mac Guaranteed Securities [Member]
Guarantor Obligations [Line Items]
Proceeds from Sale of Other Investments		38,063,000	25,674,000	30,725,000
Guarantee Fees Received		5,197,000	7,520,000	7,592,000
Payments to Acquire Loans and Leases Held-for-investment		8,933,000	7,471,000	3,456,000
Collateralized Loan Obligations [Member] | Variable Interest Entity, Not Primary Beneficiary | Financial Guarantee [Member]
Guarantor Obligations [Line Items]
Guarantor Obligations, Current Carrying Value		15,800,000	12,300,000
Deconsolidiation Of Transferred Assets Securitized, Increase To Guarantee And Commitment Obligations	$ 5,900,000
Collateralized Loan Obligations [Member] | Farmer Mac Guaranteed Securities AgVantage [Member] | Financial Guarantee [Member]
Guarantor Obligations [Line Items]
Securitization Interests Continued To Be Held By Transferor, Weighted Average Remaining Maturity		4 years 8 months 12 days	5 years 3 months 18 days
Collateralized Loan Obligations [Member] | Farmer Mac Guaranteed Securities [Member] | Financial Guarantee [Member]
Guarantor Obligations [Line Items]
Securitization Interests Continued To Be Held By Transferor, Weighted Average Remaining Maturity		13 years 4 months 24 days	13 years 3 months 18 days