Loans and Allowance for Losses and Concentrations of Credit Risk - Certain Loans Acquired Delinquencies and Net Credit Losses (Details) - USD ($) $ in Thousands		9 Months Ended
		Sep. 30, 2015		Sep. 30, 2014	Dec. 31, 2014
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	[2]	$ 36,669	[1]		$ 18,917	[3]
Net credit losses (recoveries)		160		$ (66)
Certain Loans Acquired In Transfer Not Accounted For As Debt Securities, Subject To Be Purchased	[2]	2,100			1,800
On-balance sheet [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	[2]	17,967	[1]		18,427	[3]
Net credit losses (recoveries)		160		(66)
Off-balance sheet [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	[2]	18,702	[1]		$ 490	[3]
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] 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.

[3] 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.