Farmer Mac Guaranteed Securities and USDA Securities - Schedule of Available-for-sale Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Institutional Credit
Weighted- Average Yield
Available-for-sale, accrued interest excluded	$ 30,400	$ 32,300
Farmer Mac Guaranteed Securities
Amortized Cost
Due within one year	1,643,186
Due after one year through five years	1,821,449
Due after five years through ten years	865,954
Due after ten years	1,579,400
Debt securities, available-for-sale, amortized cost	5,909,989
Fair Value
Due within one year	1,653,306
Due after one year through five years	1,899,828
Due after five years through ten years	897,786
Due after ten years	1,687,839
Total, Fair Value	$ 6,138,759
Weighted- Average Yield
Due within one year	1.59%
Due after one year through five years	2.70%
Due after five years through ten years	2.11%
Due after ten years	2.46%
Total, Weighted-Average Yield	2.24%
Farmer Mac Guaranteed Securities | Institutional Credit
Amortized Cost
Debt securities, available-for-sale, amortized cost	$ 5,909,989	6,594,992
Fair Value
Total, Fair Value		$ 6,947,701