Accounting Policies - Supplemental Cash Flows (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
	Jun. 30, 2012	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Supplemental Cash and Non-cash Transactions [Line Items]
Interest		$ 112,663	$ 101,288	$ 78,245
Income taxes		21,500	26,568	15,174
Loans acquired and securitized as Farmer Mac Guaranteed Securities		32,736	22,406	8,594
Real Estate, Acquisitions Through Foreclosures		2,280	4,605	5,001
Purchases of Investment Securities Traded, Not Yet Settled		0	162,674	0
Consolidation of guaranteed securities from off-balance sheet to Loans Held for Investment and Debt Securities of consolidated trusts held by third parties		32,736	22,406	1,408,965
Transfer of available-for-sale Farmer Mac Guaranteed Securities to loans held for investment in consolidated trusts		0	0	5,385
Transfer of trading Farmer Mac Guaranteed Securities to loans held for investment in consolidated trusts		0	0	451,448
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	460,261	0	414,462
Transfer of Loans Held-for-sale to Portfolio Loans		$ 0	$ 878,798	$ 0
Maximum [Member]
Supplemental Cash and Non-cash Transactions [Line Items]
Cash Equivalent Maturity Period		3 months