Farmer Mac Guaranteed Securities and USDA Securities - Schedule of Available-for-sale Securities (Details) - Farmer Mac Guaranteed Securities $ in Thousands	Jun. 30, 2020 USD ($)
Amortized Cost
Due within one year	$ 1,435,445
Due after one year through five years	3,434,770
Due after five years through ten years	1,147,366
Due after ten years	1,522,363
Amortized Cost	7,539,944
Fair Value
Due within one year	1,438,585
Due after one year through five years	3,557,439
Due after five years through ten years	1,232,206
Due after ten years	1,670,157
Total	$ 7,898,387
Weighted- Average Yield
Due within one year	1.34%
Due after one year through five years	2.34%
Due after five years through ten years	2.34%
Due after ten years	2.67%
Total	2.22%