Guarantees - Off-Balance Sheet Guaranteed Securities (Details) - Unconsolidated VIEs: - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Guarantor Obligations [Line Items]
Total off-balance sheet Farmer Mac Guaranteed Securities	$ 504,105	$ 813,444
Farm & Ranch
Guarantor Obligations [Line Items]
Total off-balance sheet Farmer Mac Guaranteed Securities	107,322	135,862
USDA Guarantees
Guarantor Obligations [Line Items]
Total off-balance sheet Farmer Mac Guaranteed Securities	389,216	367,684
Institutional Credit
Guarantor Obligations [Line Items]
Total off-balance sheet Farmer Mac Guaranteed Securities	7,567	9,898
Revolving Credit Facility | Institutional Credit
Guarantor Obligations [Line Items]
Total off-balance sheet Farmer Mac Guaranteed Securities	$ 0	$ 300,000