Accounting Policies - Supplemental Cash Flows (Details) (USD $)	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Jan. 02, 2013
Supplemental Cash and Non-cash Transactions [Line Items]
Interest	$ 90,052,000	$ 90,588,000
Income taxes	17,000,000	16,500,000
Real Estate, Acquisitions Through Foreclosures	1,443,000	1,130,000
Loans acquired and securitized as Farmer Mac Guaranteed Securities	64,609,000	24,008,000
Purchases of Investment Securities Traded, Not Yet Settled	57,001,000	0
Consolidation of guaranteed securities from off-balance sheet to Loans Held for Investment and Debt Securities of consolidated trusts held by third parties	64,609,000	24,008,000
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	0	460,261,000
Transfer of Loans Held-for-sale to Portfolio Loans	673,991,000	0
Transfer of Loans Held-for-sale to Loans Held-for Investment, unamortized discount			$ 5,900,000
Maximum [Member]
Supplemental Cash and Non-cash Transactions [Line Items]
Cash Equivalent Maturity Period	3 months