Debt Securities, Available-for-Sale, Accrued Interest

No definition available.

Name:	agm_DebtSecuritiesAvailableForSaleAccruedInterest
Namespace Prefix:	agm_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Debt Securities, Available-for-Sale, Unpaid Principal Balance

+ References

No definition available.

+ Details

Name:	agm_DebtSecuritiesAvailableforSaleUnpaidPrincipalBalance
Namespace Prefix:	agm_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Debt Securities, Held-to-Maturity, Accrued Interest

+ References

No definition available.

+ Details

Name:	agm_DebtSecuritiesHeldToMaturityAccruedInterest
Namespace Prefix:	agm_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Debt Securities, Held-to-maturity, Fair Value, Net of Allowance

+ References

No definition available.

+ Details

Name:	agm_DebtSecuritiesHeldToMaturityFairValueNetOfAllowance
Namespace Prefix:	agm_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Debt Securities, Trading, Accrued Interest

+ References

No definition available.

+ Details

Name:	agm_DebtSecuritiesTradingAccruedInterest
Namespace Prefix:	agm_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Debt Securities, Trading, Allowance for Credit Loss

+ References

No definition available.

+ Details

Name:	agm_DebtSecuritiesTradingAllowanceForCreditLoss
Namespace Prefix:	agm_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Held-to-Maturity Unpaid Principal Balance

+ References

No definition available.

+ Details

Name:	agm_HeldtoMaturityUnpaidPrincipalBalance
Namespace Prefix:	agm_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Trading Securities Unpaid Principal Balance

+ References

No definition available.

+ Details

Name:	agm_TradingSecuritiesUnpaidPrincipalBalance
Namespace Prefix:	agm_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Trading Securities, Weighted-Average Yield

+ References

No definition available.

+ Details

Name:	agm_TradingSecuritiesWeightedAverageYield
Namespace Prefix:	agm_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27161-111563

+ Details

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

- Definition

Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27161-111563

+ Details

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

- Definition

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27161-111563

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=121558606&loc=SL82898722-210454

+ Details

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

- References

No definition available.

+ Details

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

- Definition

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(6))
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=121558606&loc=SL82898722-210454

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121553693&loc=d3e26610-111562

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27161-111563

+ Details

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

- Definition

Amount, after accumulated amortization, of debt discount (premium).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28555-108399

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28551-108399

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28567-108399

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28541-108399

Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

+ Details

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

- Definition

Amount of allowance for credit loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 50
-Paragraph 9
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121582814&loc=SL82922900-210455

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 50
-Paragraph 9
-Subparagraph (i)
-URI http://asc.fasb.org/extlink&oid=121582814&loc=SL82922900-210455

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (aaa)
-URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27161-111563

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=121558606&loc=SL82898722-210454

+ Details

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

- Definition

Amount of allowance for credit loss for debt security measured at amortized cost (held-to-maturity).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 13
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121599337&loc=SL82919249-210447

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (aaa)
-URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27232-111563

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=121599878&loc=SL82895884-210446

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 13
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=121599337&loc=SL82919249-210447

+ Details

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

- References

No definition available.

+ Details

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

- Definition

Amount of unrealized gain on investment in debt security measured at fair value with change in fair value recognized in net income (trading).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 9
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27357-111563

+ Details

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

- Definition

Amount of unrealized loss on investment in debt security measured at fair value with change in fair value recognized in net income (trading).

+ References

+ Details

Name:	us-gaap_DebtSecuritiesTradingUnrealizedLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- References

No definition available.

+ Details

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

- Definition

Amount of accumulated unrecognized gain on investment in debt security measured at amortized cost (held-to-maturity).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27232-111563

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121645371&loc=SL120269820-111563

+ Details

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

- Definition

Amount of accumulated unrealized loss on investment in debt security measured at amortized cost (held-to-maturity).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27232-111563

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5A
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=121645371&loc=SL120269820-111563

+ Details

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

- Definition

Amount, before other-than-temporary impairment (OTTI) accretion, of investment in debt securities measured at amortized cost (held-to-maturity).

+ References

No definition available.

+ Details

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

- Definition

Amount of investment in debt security measured at fair value with change in fair value recognized in net income (trading) and investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.4)
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

+ Details

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

- Definition

Amortized cost of investments in debt securities classified as trading.

+ References

No definition available.

+ Details

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

- Details

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

- Details

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

- Details

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

- Details

Name:	us-gaap_InformationByCategoryOfDebtSecurityAxis=us-gaap_HeldtomaturitySecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=agm_USDAGuaranteesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InformationByCategoryOfDebtSecurityAxis=agm_DebtSecuritiesTradingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=agm_InstitutionalCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InformationByCategoryOfDebtSecurityAxis=us-gaap_AvailableforsaleSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Farmer Mac Guaranteed Securities and USDA Securities - Schedule of On-Balance Sheet Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019	Mar. 31, 2021	Dec. 31, 2020
Farmer Mac Guaranteed Securities
Held-to-maturity:
Unpaid Principal Balance			$ 1,158,964	$ 1,175,886
Amortized Cost			1,159,015	1,175,912
Allowance for losses			(223)	(120)
Unrealized Gains			20,379	25,259
Unrealized Losses			(5,129)	(61)
Fair Value			1,174,042	1,200,990
Available-for-sale:
Amortized Cost			6,511,776
Fair Value			6,763,209
USDA Securities:
Trading:
Fair Value			5,578	6,695
Farmer Mac Guaranteed Securities and USDA Securities
Held-to-maturity:
Unpaid Principal Balance			3,623,767	3,622,436
Amortized Cost			3,648,515	3,649,538
Allowance for losses			(223)	(120)
Unrealized Gains			150,154	183,007
Unrealized Losses			(5,526)	(621)
Fair Value			3,792,920	3,831,804
Held-to-Maturity Securities \| Farmer Mac Guaranteed Securities
Held-to-maturity:
Unamortized Premium/(Discount)			51	26
Available-for-sale:
Unamortized Premium/(Discount)			51	26
Trading:
Unamortized Premium/(Discount)			51	26
Held-to-Maturity Securities \| Farmer Mac Guaranteed Securities and USDA Securities
Held-to-maturity:
Unamortized Premium/(Discount)			24,748	27,102
Available-for-sale:
Unamortized Premium/(Discount)			24,748	27,102
Trading:
Unamortized Premium/(Discount)			24,748	27,102
USDA Guarantees
Held-to-maturity:
Unamortized Premium/(Discount)			100	100
Available-for-sale:
Unamortized Premium/(Discount)			100	100
Trading:
Unamortized Premium/(Discount)			100	100
USDA Guarantees \| Farmer Mac Guaranteed Securities
Held-to-maturity:
Unpaid Principal Balance			32,050	34,456
Amortized Cost			32,128	34,537
Allowance for losses			0	0
Unrealized Gains			1,385	1,273
Unrealized Losses			0	0
Fair Value			33,513	35,810
USDA Guarantees \| USDA Securities:
Held-to-maturity:
Unpaid Principal Balance			2,464,803	2,446,550
Amortized Cost			2,489,500	2,473,626
Allowance for losses			0	0
Unrealized Gains			129,775	157,748
Unrealized Losses			(397)	(560)
Fair Value			2,618,878	2,630,814
Trading:
Unpaid Principal Balance			5,344	6,413
Amortized Cost			5,509	6,611
Allowance for losses			0	0
Unrealized Gains	$ 72	$ 84
Unrealized Losses	$ (3)	$ 0
Fair Value			$ 5,578	$ 6,695
Trading securities, weighted-average yield			5.03%	5.05%
USDA Guarantees \| Held-to-Maturity Securities \| Farmer Mac Guaranteed Securities
Held-to-maturity:
Unamortized Premium/(Discount)			$ 78	$ 81
Available-for-sale:
Unamortized Premium/(Discount)			78	81
Trading:
Unamortized Premium/(Discount)			78	81
USDA Guarantees \| Held-to-Maturity Securities \| USDA Securities:
Held-to-maturity:
Unamortized Premium/(Discount)			24,697	27,076
Available-for-sale:
Unamortized Premium/(Discount)			24,697	27,076
Trading:
Unamortized Premium/(Discount)			24,697	27,076
USDA Guarantees \| Trading \| USDA Securities:
Held-to-maturity:
Unamortized Premium/(Discount)			165	198
Available-for-sale:
Unamortized Premium/(Discount)			165	198
Trading:
Unamortized Premium/(Discount)			165	198
AgVantage Securities
Trading:
Available-for-sale, accrued interest excluded			32,100	32,300
Held-to-maturity, accrued interest excluded			36,900	44,700
Trading securities, accrued interest excluded			100	200
AgVantage Securities \| Farmer Mac Guaranteed Securities
Held-to-maturity:
Unpaid Principal Balance			1,126,914	1,141,430
Amortized Cost			1,126,887	1,141,375
Allowance for losses			(223)	(120)
Unrealized Gains			18,994	23,986
Unrealized Losses			(5,129)	(61)
Fair Value			1,140,529	1,165,180
Available-for-sale:
Unpaid Principal Balance			6,510,351	6,593,518
Amortized Cost			6,511,776	6,594,992
Allowance for losses			(127)	(310)
Unrealized Gains			261,178	368,257
Unrealized Losses			(9,618)	(15,238)
Fair Value			6,763,209	6,947,701
AgVantage Securities \| Held-to-Maturity Securities \| Farmer Mac Guaranteed Securities
Held-to-maturity:
Unamortized Premium/(Discount)			(27)	(55)
Available-for-sale:
Unamortized Premium/(Discount)			(27)	(55)
Trading:
Unamortized Premium/(Discount)			(27)	(55)
AgVantage Securities \| Available-for-Sale Securities \| Farmer Mac Guaranteed Securities
Held-to-maturity:
Unamortized Premium/(Discount)			1,425	1,474
Available-for-sale:
Unamortized Premium/(Discount)			1,425	1,474
Trading:
Unamortized Premium/(Discount)			$ 1,425	$ 1,474