Off-Balance Sheet Guarantees and Long Term Standby Purchase Commitments - Maximum Exposure (Details) (Variable Interest Entity, Not Primary Beneficiary, USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Rural Utilities Farmer Mac Guaranteed Securities AgVantage [Member]
Guarantor Obligations [Line Items]
Maximum principal amount of potential undiscounted future payments	$ 16,270	$ 16,271
Farmer Mac II Guaranteed Securities
Guarantor Obligations [Line Items]
Maximum principal amount of potential undiscounted future payments	36,762	42,088
Farmer Mac I Guaranteed Securities
Guarantor Obligations [Line Items]
Maximum principal amount of potential undiscounted future payments	1,010,507	621,871
Farmer Mac I Guaranteed Securities AgVantage [Member]
Guarantor Obligations [Line Items]
Maximum principal amount of potential undiscounted future payments	970,000	970,000
Farmer Mac Guaranteed Securities
Guarantor Obligations [Line Items]
Maximum principal amount of potential undiscounted future payments	$ 2,033,539	$ 1,650,230