Farmer Mac Guaranteed Securities and USDA Securities - Schedule of Held-to-maturity Securities (Details) - Farmer Mac Guaranteed Securities and USDA Securities [Member] - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Amortized Cost
Due within one year	$ 539,516
Due after one year through five years	1,094,543
Due after five years through ten years	203,660
Due after ten years	1,869,834
Amortized Cost	3,707,553	$ 4,262,792
Fair Value
Due within one year	538,274
Due after one year through five years	1,108,105
Due after five years through ten years	203,644
Due after ten years	1,874,851
Total	$ 3,724,874	$ 4,191,352
Weighted- Average Yield
Due within one year	2.24%
Due after one year through five years	3.32%
Due after five years through ten years	3.48%
Due after ten years	3.63%
Total	3.33%