Farmer Mac Guaranteed Securities and USDA Securities - Schedule of Available-for-sale Securities (Details) - Farmer Mac Guaranteed Securities $ in Thousands	Mar. 31, 2021 USD ($)
Amortized Cost
Due within one year	$ 1,289,615
Due after one year through five years	2,992,792
Due after five years through ten years	986,013
Due after ten years	1,243,356
Amortized cost of available-for-sale investment securities	6,511,776
Fair Value
Due within one year	1,293,004
Due after one year through five years	3,122,713
Due after five years through ten years	1,058,037
Due after ten years	1,289,455
Total, Fair Value	$ 6,763,209
Weighted- Average Yield
Due within one year	1.43%
Due after one year through five years	2.40%
Due after five years through ten years	2.31%
Due after ten years	2.75%
Total, Weighted-Average Yield	2.28%