Farmer Mac Guaranteed Securities and USDA Guaranteed Securities - Schedule of Held-to-maturity Securities (Details) $ in Thousands	Sep. 30, 2016 USD ($)
Farmer Mac Guaranteed Securities and USDA Securities [Member]
Held-to-Maturity Securities, Debt Maturities, Weighted Average Yield, Single Maturity Date [Abstract]
Held-to-maturity Securities, Debt Maturities, after Five Through Ten Years, Weighted Average Yield	3.24%
Farmer Mac Guaranteed Securities [Member]
Held-to-maturity Securities, Debt Maturities, Single Maturity Date, Amortized Cost Basis [Abstract]
Held-to-maturity Securities, Debt Maturities, within One Year, Net Carrying Amount	$ 407,942
Held-to-maturity Securities, Debt Maturities, after One Through Five Years, Net Carrying Amount	693,616
Held-to-maturity Securities, Debt Maturities, after Five Through Ten Years, Net Carrying Amount	52,088
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	1,153,646
Held-to-maturity Securities, Debt Maturities, Single Maturity Date, Fair Value [Abstract]
Held-to-maturity Securities, Debt Maturities, Next Twelve Months, Fair Value	408,699
Held-to-maturity Securities, Debt Maturities, Year Two Through Five, Fair Value	701,844
Held-to-maturity Securities, Debt Maturities, Year Six Through Ten, Fair Value	55,411
Held-to-maturity Securities, Fair Value	$ 1,165,954
Held-to-Maturity Securities, Debt Maturities, Weighted Average Yield, Single Maturity Date [Abstract]
Held-to-Maturity Securities, Debt Maturities, Next Twelve Months, Weighted-Average Yield	1.60%
Held-to-Maturity Securities, Debt Maturities, Year Two Through Five, Weighted-Average Yield	1.94%
Held-to-Maturity Securities, Debt Maturities, Weighted-Average Yield	1.88%