Loans and Allowance for Losses and Concentrations of Credit Risk - Certain Loans Acquired Delinquencies and Net Credit Losses (Details) (USD $)	3 Months Ended
	Mar. 31, 2015		Mar. 31, 2014	Dec. 31, 2014
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	$ 32,101,000	[1]		$ 18,917,000	[2]
Net credit losses (recoveries)	0		32,000
Certain Loans Acquired In Transfer Not Accounted For As Debt Securities, Subject To Be Purchased	3,100,000	[3]		1,800,000	[3]
On-balance sheet [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	30,151,000	[1]		18,427,000	[2]
Net credit losses (recoveries)	0		32,000
Off-balance sheet [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	1,950,000	[1]		490,000	[2]
Net credit losses (recoveries)	$ 0		$ 0

[1] Amounts represent unpaid principal balance of risk-rated loans, which is the basis Farmer Mac uses to analyze its portfolio, and recorded investment of past due loans.

[2] (1) Amounts represent unpaid principal balance of risk-rated loans, which is the basis Farmer Mac uses to analyze its portfolio, and recorded investment of past due loans.

[3] Includes loans and loans underlying off-balance sheet Farm & Ranch Guaranteed Securities and LTSPCs that are 90 days or more past due, in foreclosure, or in bankruptcy, excluding loans performing under either their original loan terms or a court-approved bankruptcy plan.