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, 2017		Sep. 30, 2016	Dec. 31, 2016
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	[2]	$ 66,381	[1]		$ 21,038	[3]
Net credit losses (recoveries)		(520)		$ 154
Certain Loans Acquired In Transfer Not Accounted For As Debt Securities, Subject To Be Purchased	[2]	0			100
On-balance sheet [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	[2]	65,105	[1]		19,757	[3]
Net credit losses (recoveries)		(520)		154
Off-balance sheet [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Financing Receivable, Recorded Investment, Past Due	[2]	1,276	[1]		$ 1,281	[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 with at least one missed payment, 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.