Farmer Mac Guaranteed Securities and USDA Securities - Schedule of Held-to-maturity Securities (Details) - Farmer Mac Guaranteed Securities and USDA Securities - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Amortized Cost
Due within one year	$ 452,256
Due after one year through five years	1,045,189
Due after five years through ten years	207,706
Due after ten years	1,974,460
Amortized Cost	3,679,611	$ 4,262,792
Fair Value
Due within one year	452,712
Due after one year through five years	1,061,151
Due after five years through ten years	210,690
Due after ten years	2,024,631
Total	$ 3,749,184	$ 4,191,352
Weighted- Average Yield
Due within one year	2.51%
Due after one year through five years	3.23%
Due after five years through ten years	3.40%
Due after ten years	3.56%
Total	3.33%