Farmer Mac Guaranteed Securities and USDA Securities - Schedule of Available-for-sale Securities (Details) - Farmer Mac Guaranteed Securities [Member] $ in Thousands	Jun. 30, 2019 USD ($)
Amortized Cost
Due within one year	$ 586,896
Due after one year through five years	3,432,197
Due after five years through ten years	1,347,781
Due after ten years	1,556,441
Amortized Cost	6,923,315
Fair Value
Due within one year	586,944
Due after one year through five years	3,466,313
Due after five years through ten years	1,383,218
Due after ten years	1,599,193
Total	$ 7,035,668
Weighted- Average Yield
Due within one year	2.92%
Due after one year through five years	3.09%
Due after five years through ten years	3.26%
Due after ten years	3.55%
Total	3.21%