Guarantees - Off-Balance Sheet Guaranteed Securities (Details) - Unconsolidated VIEs: - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Guarantor Obligations [Line Items]
Total off-balance sheet Farmer Mac Guaranteed Securities	$ 383,022	$ 504,105
Farm & Ranch
Guarantor Obligations [Line Items]
Total off-balance sheet Farmer Mac Guaranteed Securities	79,312	107,322
USDA Guarantees
Guarantor Obligations [Line Items]
Total off-balance sheet Farmer Mac Guaranteed Securities	299,298	389,216
AgVantage Securities
Guarantor Obligations [Line Items]
Total off-balance sheet Farmer Mac Guaranteed Securities	$ 4,412	$ 7,567