Farmer Mac Guaranteed Securities and USDA Securities - Schedule of Held-to-maturity Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Institutional Credit
Weighted- Average Yield
Held-to-maturity, accrued interest excluded	$ 37,500	$ 44,700
Farmer Mac Guaranteed Securities and USDA Securities
Amortized Cost
Due within one year	1,442,247
Due after one year through five years	834,861
Due after five years through ten years	248,841
Due after ten years	2,179,744
Amortized Cost	4,705,693	$ 3,649,538
Fair Value
Due within one year	1,443,316
Due after one year through five years	840,125
Due after five years through ten years	257,529
Due after ten years	2,257,175
Total	$ 4,798,145
Weighted- Average Yield
Due within one year	0.74%
Due after one year through five years	2.08%
Due after five years through ten years	2.79%
Due after ten years	3.17%
Total	2.19%