Guarantees - Narrative (Details) - USD ($)	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Guarantor Obligations [Line Items]
Minimum term of guarantees	1 year
Maximum term of gurantees	30 years
Farm & Ranch Loans and USDA Guarantees
Guarantor Obligations [Line Items]
Commitments to purchase	$ 125,800,000	$ 65,100,000
Rural Utilities Loans
Guarantor Obligations [Line Items]
Commitments to purchase	0
Guarantee and commitment obligation
Guarantor Obligations [Line Items]
Total off-balance sheet Farmer Mac Guaranteed Securities	3,300,000,000	3,500,000,000
Guarantee obligations issued prior to January 1, 2003
Guarantor Obligations [Line Items]
Total off-balance sheet Farmer Mac Guaranteed Securities	$ 10,800,000	$ 15,500,000

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Term of Guarantees, Minimum

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Maximum potential amount of future payments (undiscounted) the guarantor could be required to make under the guarantee or each group of similar guarantees before reduction for potential recoveries under recourse or collateralization provisions.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
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-Section 50
-Paragraph 4
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Reflects the carrying amount of loans and leases for which agreements to acquire or dispose exist.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
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