Guarantees - Off-Balance Sheet Guaranteed Securities (Details) - Variable Interest Entity, Not Primary Beneficiary - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Guarantor Obligations [Line Items]
Total off-balance sheet Farmer Mac Guaranteed Securities	$ 426,602	$ 504,105
Farm & Ranch
Guarantor Obligations [Line Items]
Total off-balance sheet Farmer Mac Guaranteed Securities	90,225	107,322
USDA Guarantees
Guarantor Obligations [Line Items]
Total off-balance sheet Farmer Mac Guaranteed Securities	330,309	389,216
Institutional Credit
Guarantor Obligations [Line Items]
Total off-balance sheet Farmer Mac Guaranteed Securities	$ 6,068	$ 7,567