Farmer Mac Guaranteed Securities and USDA Securities - Schedule of Available-for-sale Securities (Details) - Farmer Mac Guaranteed Securities $ in Thousands	Dec. 31, 2020 USD ($)
Amortized Cost
Due within one year	$ 1,212,051
Due after one year through five years	2,861,186
Due after five years through ten years	1,016,527
Due after ten years	1,505,228
Amortized cost of available-for-sale investment securities	6,594,992
Fair Value
Due within one year	1,216,431
Due after one year through five years	2,971,603
Due after five years through ten years	1,092,170
Due after ten years	1,667,497
Total, Fair Value	$ 6,947,701
Weighted- Average Yield
Due within one year	1.52%
Due after one year through five years	2.41%
Due after five years through ten years	2.36%
Due after ten years	2.55%
Total, Weighted-Average Yield	2.27%