XML 50 R56.htm IDEA: XBRL DOCUMENT v2.4.1.9
Mortgage Loans Individually Impaired Loans (Details) (USD $)
In Millions, unless otherwise specified
Mar. 31, 2015
Dec. 31, 2014
Financing Receivable, Impaired [Line Items]    
Individually impaired loans with related allowance recorded: unpaid principal balance $ 171,980us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance $ 177,630us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
Individually impaired loans with related allowance recorded: total recorded investment 162,530us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment 168,510us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
Related allowance for loan losses 28,808us-gaap_ImpairedFinancingReceivableRelatedAllowance 31,375us-gaap_ImpairedFinancingReceivableRelatedAllowance
Individually impaired loans with no related allowance recorded: unpaid principal balance 24,987us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance 22,563us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
Individually impaired loans with no related allowance recorded: total recorded investment 22,156us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment 19,676us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
Total individually impaired loans: unpaid principal balance 196,967us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance 200,193us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance
Total individually impaired loans: total recorded investment 184,686us-gaap_ImpairedFinancingReceivableRecordedInvestment 188,186us-gaap_ImpairedFinancingReceivableRecordedInvestment
Interest Receivable [Member]    
Financing Receivable, Impaired [Line Items]    
Related allowance for loan losses   501us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= fnm_InterestReceivableMember
Single-Family [Member]    
Financing Receivable, Impaired [Line Items]    
Individually impaired loans with related allowance recorded: unpaid principal balance 170,770us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_SingleFamilyMember
176,400us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_SingleFamilyMember
Individually impaired loans with related allowance recorded: total recorded investment 161,313us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_SingleFamilyMember
167,269us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_SingleFamilyMember
Related allowance for loan losses 28,662us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_SingleFamilyMember
31,200us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_SingleFamilyMember
Individually impaired loans with no related allowance recorded: unpaid principal balance 24,476us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_SingleFamilyMember
21,998us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_SingleFamilyMember
Individually impaired loans with no related allowance recorded: total recorded investment 21,643us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_SingleFamilyMember
19,108us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_SingleFamilyMember
Single-Family [Member] | Interest Receivable [Member]    
Financing Receivable, Impaired [Line Items]    
Related allowance for loan losses   495us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= fnm_InterestReceivableMember
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_SingleFamilyMember
Single-Family [Member] | Primary [Member]    
Financing Receivable, Impaired [Line Items]    
Individually impaired loans with related allowance recorded: unpaid principal balance 122,873us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnm_PrimaryMortgageLoanMember
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_SingleFamilyMember
125,960us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnm_PrimaryMortgageLoanMember
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_SingleFamilyMember
Individually impaired loans with related allowance recorded: total recorded investment 116,908us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnm_PrimaryMortgageLoanMember
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_SingleFamilyMember
120,221us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnm_PrimaryMortgageLoanMember
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_SingleFamilyMember
Related allowance for loan losses 18,954us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnm_PrimaryMortgageLoanMember
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_SingleFamilyMember
20,327us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnm_PrimaryMortgageLoanMember
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_SingleFamilyMember
Individually impaired loans with no related allowance recorded: unpaid principal balance 18,139us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnm_PrimaryMortgageLoanMember
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_SingleFamilyMember
16,704us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnm_PrimaryMortgageLoanMember
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_SingleFamilyMember
Individually impaired loans with no related allowance recorded: total recorded investment 16,349us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnm_PrimaryMortgageLoanMember
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_SingleFamilyMember
14,876us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnm_PrimaryMortgageLoanMember
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_SingleFamilyMember
Single-Family [Member] | Primary [Member] | Interest Receivable [Member]    
Financing Receivable, Impaired [Line Items]    
Related allowance for loan losses   309us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= fnm_InterestReceivableMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnm_PrimaryMortgageLoanMember
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_SingleFamilyMember
Single-Family [Member] | Government [Member]    
Financing Receivable, Impaired [Line Items]    
Individually impaired loans with related allowance recorded: unpaid principal balance 282us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnm_GovernmentMortgageLoanMember
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_SingleFamilyMember
281us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnm_GovernmentMortgageLoanMember
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_SingleFamilyMember
Individually impaired loans with related allowance recorded: total recorded investment 286us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnm_GovernmentMortgageLoanMember
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_SingleFamilyMember
285us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnm_GovernmentMortgageLoanMember
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_SingleFamilyMember
Related allowance for loan losses 58us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnm_GovernmentMortgageLoanMember
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_SingleFamilyMember
46us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnm_GovernmentMortgageLoanMember
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_SingleFamilyMember
Individually impaired loans with no related allowance recorded: unpaid principal balance 60us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnm_GovernmentMortgageLoanMember
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_SingleFamilyMember
61us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnm_GovernmentMortgageLoanMember
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_SingleFamilyMember
Individually impaired loans with no related allowance recorded: total recorded investment 55us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnm_GovernmentMortgageLoanMember
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_SingleFamilyMember
57us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnm_GovernmentMortgageLoanMember
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_SingleFamilyMember
Single-Family [Member] | Government [Member] | Interest Receivable [Member]    
Financing Receivable, Impaired [Line Items]    
Related allowance for loan losses   12us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= fnm_InterestReceivableMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnm_GovernmentMortgageLoanMember
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_SingleFamilyMember
Single-Family [Member] | Alt-A [Member]    
Financing Receivable, Impaired [Line Items]    
Individually impaired loans with related allowance recorded: unpaid principal balance 33,719us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnm_AltAMortgageLoansMember
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_SingleFamilyMember
35,492us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnm_AltAMortgageLoansMember
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_SingleFamilyMember
Individually impaired loans with related allowance recorded: total recorded investment 30,954us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnm_AltAMortgageLoansMember
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_SingleFamilyMember
32,816us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnm_AltAMortgageLoansMember
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_SingleFamilyMember
Related allowance for loan losses 6,935us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnm_AltAMortgageLoansMember
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_SingleFamilyMember
7,778us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnm_AltAMortgageLoansMember
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_SingleFamilyMember
Individually impaired loans with no related allowance recorded: unpaid principal balance 4,737us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnm_AltAMortgageLoansMember
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_SingleFamilyMember
3,993us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnm_AltAMortgageLoansMember
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_SingleFamilyMember
Individually impaired loans with no related allowance recorded: total recorded investment 3,881us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnm_AltAMortgageLoansMember
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_SingleFamilyMember
3,119us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnm_AltAMortgageLoansMember
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_SingleFamilyMember
Single-Family [Member] | Alt-A [Member] | Interest Receivable [Member]    
Financing Receivable, Impaired [Line Items]    
Related allowance for loan losses   136us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= fnm_InterestReceivableMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnm_AltAMortgageLoansMember
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_SingleFamilyMember
Single-Family [Member] | Other [Member]    
Financing Receivable, Impaired [Line Items]    
Individually impaired loans with related allowance recorded: unpaid principal balance 13,896us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnm_OtherMortgageLoanMember
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_SingleFamilyMember
14,667us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnm_OtherMortgageLoanMember
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_SingleFamilyMember
Individually impaired loans with related allowance recorded: total recorded investment 13,165us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnm_OtherMortgageLoanMember
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_SingleFamilyMember
13,947us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnm_OtherMortgageLoanMember
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_SingleFamilyMember
Related allowance for loan losses 2,715us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnm_OtherMortgageLoanMember
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_SingleFamilyMember
3,049us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnm_OtherMortgageLoanMember
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_SingleFamilyMember
Individually impaired loans with no related allowance recorded: unpaid principal balance 1,540us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnm_OtherMortgageLoanMember
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_SingleFamilyMember
1,240us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnm_OtherMortgageLoanMember
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_SingleFamilyMember
Individually impaired loans with no related allowance recorded: total recorded investment 1,358us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnm_OtherMortgageLoanMember
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_SingleFamilyMember
1,056us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnm_OtherMortgageLoanMember
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_SingleFamilyMember
Single-Family [Member] | Other [Member] | Interest Receivable [Member]    
Financing Receivable, Impaired [Line Items]    
Related allowance for loan losses   38us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= fnm_InterestReceivableMember
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= fnm_OtherMortgageLoanMember
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_SingleFamilyMember
Multifamily [Member]    
Financing Receivable, Impaired [Line Items]    
Individually impaired loans with related allowance recorded: unpaid principal balance 1,210us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_MultifamilyMember
1,230us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_MultifamilyMember
Individually impaired loans with related allowance recorded: total recorded investment 1,217us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_MultifamilyMember
1,241us-gaap_ImpairedFinancingReceivableWithRelatedAllowanceRecordedInvestment
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_MultifamilyMember
Related allowance for loan losses 146us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_MultifamilyMember
175us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_MultifamilyMember
Individually impaired loans with no related allowance recorded: unpaid principal balance 511us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_MultifamilyMember
565us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceUnpaidPrincipalBalance
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_MultifamilyMember
Individually impaired loans with no related allowance recorded: total recorded investment 513us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_MultifamilyMember
568us-gaap_ImpairedFinancingReceivableWithNoRelatedAllowanceRecordedInvestment
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_MultifamilyMember
Multifamily [Member] | Interest Receivable [Member]    
Financing Receivable, Impaired [Line Items]    
Related allowance for loan losses   $ 6us-gaap_ImpairedFinancingReceivableRelatedAllowance
/ us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis
= fnm_InterestReceivableMember
/ us-gaap_StatementBusinessSegmentsAxis
= fnm_MultifamilyMember