FINANCIAL DERIVATIVES - Hedged Items in Fair Value Hedging Relationships (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Available-for-Sale Securities
HedgedItemsinFairValueHedgingRelationship [Line Items]
Carrying Amount of Hedged Assets/(Liabilities)	$ 1,261,144	$ 1,251,386
Hedged Asset	(116,156)	(88,635)
Loans
HedgedItemsinFairValueHedgingRelationship [Line Items]
Carrying Amount of Hedged Assets/(Liabilities)	1,692,131	1,699,361
Hedged Asset	(352,653)	(305,592)
Notes Payable
HedgedItemsinFairValueHedgingRelationship [Line Items]
Carrying Amount of Hedged Assets/(Liabilities)	(13,327,828)	(13,350,111)
Hedged Liability	305,907	250,418
Farmer Mac Guaranteed Securities
HedgedItemsinFairValueHedgingRelationship [Line Items]
Carrying Amount of Hedged Assets/(Liabilities)	5,432,676	5,497,948
Hedged Asset	$ (338,180)	$ (257,436)

[Line Items] for HedgedItemsinFairValueHedgingRelationship [Table]

No definition available.

Name:	agm_HedgedItemsinFairValueHedgingRelationshipLineItems
Namespace Prefix:	agm_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of hedged item in hedging relationship. Excludes hedged asset or liability.

+ References

No definition available.

+ Details

Name:	us-gaap_DerivativeAmountOfHedgedItem
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of cumulative increase (decrease) in fair value of hedged asset in fair value hedge, attributable to hedged risk.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 181
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480401/815-10-55-181

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4EE
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480434/815-10-50-4EE

+ Details

Name:	us-gaap_HedgedAssetFairValueHedgeCumulativeIncreaseDecrease
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of cumulative increase (decrease) in fair value of hedged liability in fair value hedge, attributable to hedged risk.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4EE
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480434/815-10-50-4EE

+ Details

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

- Details

Name:	us-gaap_BalanceSheetLocationAxis=agm_DebtSecuritiesAvailableForSaleMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BalanceSheetLocationAxis=us-gaap_LoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BalanceSheetLocationAxis=us-gaap_LongTermDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: