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Minimum Days/Months Past Due of Single Family Nonaccrual Loans

No definition available.

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Represents premiums over or discounts from face amounts of loans that are being amortized into income as an adjustment to yield and fair value adjustments.

No definition available.

Name:	fnm_MortgageLoansCostBasisAndFairValueAdjustmentsNet
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Data Type:	xbrli:monetaryItemType
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Period Type:	instant

Represents principal amount outstanding of mortgage loans.

No definition available.

Name:	fnm_MortgageLoansOnRealEstateUnpaidPrincipalBalance
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Data Type:	xbrli:monetaryItemType
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Recorded investment of consumer mortgage loans receivables secured by residential real estate properties for which formal foreclosure proceedings are in process.

No definition available.

Name:	fnm_MortgageLoansinProcessofForeclosureAmount
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The reserve to cover probable credit losses related to specifically identified fixed maturity real estate loans as well as probable credit losses inherent in the remainder of that loan portfolio.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 310

-Section 45

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=6873192&loc=d3e21338-158488

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Data Type:	xbrli:monetaryItemType
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The amount of financing receivables reclassified to held for sale during the reporting period.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 11B

-Subparagraph (f)

-URI http://asc.fasb.org/extlink&oid=35738203&loc=SL6953423-111524

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The amount of any significant sales of financing receivables during the reporting period.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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Amount after allowance and deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements and loans held for sale.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=28367877&loc=d3e4428-111522

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.7)

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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Data Type:	xbrli:monetaryItemType
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Period Type:	instant

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Name:	us-gaap_StatementBusinessSegmentsAxis=fnm_MultifamilyMember
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