Farmer Mac Guaranteed Securities and USDA Guaranteed Securities - Schedule of Held-to-maturity Securities (Details) (Farmer Mac Guaranteed Securities [Member], USD $) In Thousands, unless otherwise specified	Mar. 31, 2015
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	$ 631,918
Held-to-maturity Securities, Debt Maturities, after One Through Five Years, Net Carrying Amount	1,135,178
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	1,767,096
Held-to-maturity Securities, Debt Maturities, Single Maturity Date, Fair Value [Abstract]
Held-to-maturity Securities, Debt Maturities, Next Twelve Months, Fair Value	632,923
Held-to-maturity Securities, Debt Maturities, Year Two Through Five, Fair Value	1,150,153
Held-to-maturity Securities, Fair Value	$ 1,783,076
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	2.73%
Held-to-Maturity Securities, Debt Maturities, Year Two Through Five, Weighted-Average Yield	2.28%
Held-to-Maturity Securities, Debt Maturities, Weighted-Average Yield	2.43%