Farmer Mac Guaranteed Securities and USDA Securities - Schedule of Available-for-sale Securities (Details) - Farmer Mac Guaranteed Securities $ in Thousands	Mar. 31, 2020 USD ($)
Amortized Cost
Due within one year	$ 1,202,779
Due after one year through five years	3,358,079
Due after five years through ten years	1,181,538
Due after ten years	1,530,907
Amortized Cost	7,273,303
Fair Value
Due within one year	1,207,673
Due after one year through five years	3,479,730
Due after five years through ten years	1,259,191
Due after ten years	1,640,758
Total	$ 7,587,352
Weighted- Average Yield
Due within one year	1.82%
Due after one year through five years	2.77%
Due after five years through ten years	2.86%
Due after ten years	3.10%
Total	2.70%