Guarantees and Commitments - Narrative (Details)	12 Months Ended
Dec. 31, 2022 USD ($) creditEnhancementAlternative	Dec. 31, 2021 USD ($)
Guarantor Obligations [Line Items]
Number of credit enhancement alternatives \| creditEnhancementAlternative	2
Minimum term of guarantees	1 year
Maximum term of gurantees	30 years
Rural Utilities Loans
Guarantor Obligations [Line Items]
Commitments to purchase	$ 0
Farm & Ranch Loans and USDA Guarantees
Guarantor Obligations [Line Items]
Commitments to purchase	9,900,000	$ 75,600,000
Guarantee and commitment obligation
Guarantor Obligations [Line Items]
Total off-balance sheet Farmer Mac Guaranteed Securities	3,900,000,000	3,800,000,000
Guarantee obligations issued prior to January 1, 2003
Guarantor Obligations [Line Items]
Total off-balance sheet Farmer Mac Guaranteed Securities	6,100,000	7,800,000
Long-Term Standby Purchase Commitments
Guarantor Obligations [Line Items]
Total off-balance sheet Farmer Mac Guaranteed Securities	$ 3,423,155,000	$ 3,191,061,000

Number Of Credit Enhancement Alternatives

No definition available.

Name:	agm_NumberOfCreditEnhancementAlternatives
Namespace Prefix:	agm_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Term of Guarantees Maximum

+ References

No definition available.

+ Details

Name:	agm_TermOfGuaranteesMaximum
Namespace Prefix:	agm_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Term of Guarantees, Minimum

+ References

No definition available.

+ Details

Name:	agm_TermOfGuaranteesMinimum
Namespace Prefix:	agm_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_GuaranteeObligationsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

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
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (b)(1)
-URI https://asc.fasb.org/extlink&oid=124440162&loc=d3e12069-110248

+ Details

Name:	us-gaap_GuaranteeObligationsMaximumExposure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Reflects the carrying amount of loans and leases for which agreements to acquire or dispose exist.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 825
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=126941378&loc=d3e61044-112788

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 825
-Section 50
-Paragraph 2
-URI https://asc.fasb.org/extlink&oid=126941378&loc=d3e61082-112788

+ Details

Name:	us-gaap_LoansAndLeasesReceivableCommitmentsToPurchaseOrSell
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	srt_ProductOrServiceAxis=agm_RuralUtilitiesLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ProductOrServiceAxis=agm_FarmRanchLoansAndUSDAGuaranteesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	agm_UnrecordedMaximumPotentialExposureOnGuaranteesAxis=agm_GuaranteeobligationsissuedafterJanuary12003Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	agm_UnrecordedMaximumPotentialExposureOnGuaranteesAxis=agm_GuaranteeObligationsIssuedPriorToJanuary12003Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_GuaranteeObligationsByNatureAxis=agm_LongTermStandbyPurchaseCommitmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: