Farmer Mac Guaranteed Securities and USDA Securities - Schedule of Held-to-maturity Securities (Details) - Farmer Mac Guaranteed Securities and USDA Securities - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Amortized Cost
Due within one year	$ 655,928
Due after one year through five years	840,702
Due after five years through ten years	210,888
Due after ten years	2,010,616
Amortized Cost	3,718,134	$ 3,679,611
Fair Value
Due within one year	660,512
Due after one year through five years	869,401
Due after five years through ten years	216,447
Due after ten years	2,070,476
Total	$ 3,816,836	$ 3,749,184
Weighted- Average Yield
Due within one year	2.57%
Due after one year through five years	3.27%
Due after five years through ten years	3.34%
Due after ten years	3.52%
Total	3.29%