Farmer Mac Guaranteed Securities and USDA Guaranteed Securities - Schedule of Held-to-maturity Securities (Details) - Farmer Mac Guaranteed Securities [Member] $ in Thousands	Sep. 30, 2015 USD ($)
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	$ 632,791
Held-to-maturity Securities, Debt Maturities, after One Through Five Years, Net Carrying Amount	643,362
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	1,276,153
Held-to-maturity Securities, Debt Maturities, Single Maturity Date, Fair Value [Abstract]
Held-to-maturity Securities, Debt Maturities, Next Twelve Months, Fair Value	634,917
Held-to-maturity Securities, Debt Maturities, Year Two Through Five, Fair Value	656,373
Held-to-maturity Securities, Fair Value	$ 1,291,290
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	2.30%
Held-to-Maturity Securities, Debt Maturities, Year Two Through Five, Weighted-Average Yield	2.19%
Held-to-Maturity Securities, Debt Maturities, Weighted-Average Yield	2.24%