XML 34 R71.htm IDEA: XBRL DOCUMENT v2.4.1.9
Short-Term Borrowings and Long-Term Debt Short-term Debt (Details) (USD $)
Mar. 31, 2015
Dec. 31, 2014
Short-term Borrowings [Line Items]    
Federal funds purchased and securities sold under agreements to repurchase $ 87,000,000us-gaap_FederalFundsPurchasedAndSecuritiesSoldUnderAgreementsToRepurchase $ 50,000,000us-gaap_FederalFundsPurchasedAndSecuritiesSoldUnderAgreementsToRepurchase
Federal funds purchased and securities sold under agreements to repurchase, weighted-average interest rate 0.00%fnm_FederalFundsPurchasedAndSecuritiesSoldUnderAgreementsToRepurchaseWeightedAverageInterestRate 0.00%fnm_FederalFundsPurchasedAndSecuritiesSoldUnderAgreementsToRepurchaseWeightedAverageInterestRate
Short-term debt, outstanding 100,812,000,000us-gaap_ShortTermBorrowings 106,572,000,000us-gaap_ShortTermBorrowings
Short-term debt, weighted-average interest rate 0.14%us-gaap_ShortTermDebtWeightedAverageInterestRate 0.11%us-gaap_ShortTermDebtWeightedAverageInterestRate
Secured uncommitted line of credit [Member]    
Short-term Borrowings [Line Items]    
Line of credit maximum borrowing capacity 15,000,000,000.0us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
/ us-gaap_ShortTermDebtTypeAxis
= fnm_SecuredUncommittedLineOfCreditMember
15,000,000,000.0us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
/ us-gaap_ShortTermDebtTypeAxis
= fnm_SecuredUncommittedLineOfCreditMember
Line of credit amount outstanding 0us-gaap_LineOfCredit
/ us-gaap_ShortTermDebtTypeAxis
= fnm_SecuredUncommittedLineOfCreditMember
 
Fannie Mae [Member]    
Short-term Borrowings [Line Items]    
Short-term debt, outstanding 99,349,000,000us-gaap_ShortTermBorrowings
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
105,012,000,000us-gaap_ShortTermBorrowings
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
Short-term debt, weighted-average interest rate 0.14%us-gaap_ShortTermDebtWeightedAverageInterestRate
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
0.11%us-gaap_ShortTermDebtWeightedAverageInterestRate
/ dei_LegalEntityAxis
= us-gaap_ParentCompanyMember
Consolidated Trusts [Member]    
Short-term Borrowings [Line Items]    
Short-term debt, outstanding $ 1,463,000,000us-gaap_ShortTermBorrowings
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
$ 1,560,000,000us-gaap_ShortTermBorrowings
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
Short-term debt, weighted-average interest rate 0.12%us-gaap_ShortTermDebtWeightedAverageInterestRate
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
0.09%us-gaap_ShortTermDebtWeightedAverageInterestRate
/ dei_LegalEntityAxis
= us-gaap_VariableInterestEntityPrimaryBeneficiaryMember