Farmer Mac Guaranteed Securities and USDA Guaranteed Securities - Schedule of Held-to-maturity Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Farmer Mac Guaranteed Securities and USDA Securities [Member]
Held-to-maturity Securities, Debt Maturities, Single Maturity Date, Amortized Cost Basis [Abstract]
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	$ 4,203,812	$ 3,158,456
Held-to-maturity Securities, Debt Maturities, Single Maturity Date, Fair Value [Abstract]
Held-to-maturity Securities, Fair Value	$ 4,137,000	3,066,644
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	3.04%
Held-to-Maturity Securities, Debt Maturities, After Ten Years, Weighted-Average Yield	3.32%
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	$ 855,465
Held-to-maturity Securities, Debt Maturities, after One Through Five Years, Net Carrying Amount	1,316,883
Held-to-maturity Securities, Debt Maturities, after Five Through Ten Years, Net Carrying Amount	188,751
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	2,137,786	1,149,231
Held-to-maturity Securities, Debt Maturities, Single Maturity Date, Fair Value [Abstract]
Held-to-maturity Securities, Debt Maturities, Next Twelve Months, Fair Value	855,175
Held-to-maturity Securities, Debt Maturities, Year Two Through Five, Fair Value	1,315,234
Held-to-maturity Securities, Debt Maturities, Year Six Through Ten, Fair Value	182,992
Held-to-maturity Securities, Fair Value	$ 2,137,327	$ 1,153,009
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	1.80%
Held-to-Maturity Securities, Debt Maturities, Year Two Through Five, Weighted-Average Yield	2.16%
Held-to-Maturity Securities, Debt Maturities, Weighted-Average Yield	2.62%
Held-to-maturity Securities, Debt Maturities, after Ten Years, Net Carrying Amount	$ 1,842,713
Held-to-maturity Securities, Debt Maturities, after Ten Years, Fair Value	$ 1,783,599