Financial Guarantees Financial Guarantees and Maximum Recovery (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended			9 Months Ended			12 Months Ended
	Sep. 30, 2014		Sep. 30, 2013	Sep. 30, 2014		Sep. 30, 2013	Dec. 31, 2013
Financial Guarantees and Maximum Recovery [Line Items]
Guarantees Fair Value Investments In Securities	$ 865			$ 865			$ 1,100
Maximum Exposure	40,534	[1]		40,534	[1]		49,915	[1]
Guaranty Obligation	404			404			485
Maximum Recovery	14,550	[2]		14,550	[2]		15,066	[2]
Non-consolidated Fannie Mae MBS [Member] | Unconsolidated VIEs [Member]
Financial Guarantees and Maximum Recovery [Line Items]
Maximum Exposure	17,728	[1]		17,728	[1]		19,317	[1]
Guaranty Obligation	215			215			232
Maximum Recovery	10,062	[2]		10,062	[2]		10,541	[2]
Other guaranty arrangements [Member] | Unconsolidated VIEs [Member]
Financial Guarantees and Maximum Recovery [Line Items]
Maximum Exposure	22,806	[1],[3]		22,806	[1],[3]		30,598	[1],[3]
Guaranty Obligation	189	[3]		189	[3]		253	[3]
Maximum Recovery	$ 4,488	[2],[3]		$ 4,488	[2],[3]		$ 4,525	[2],[3]
Minimum [Member]
Financial Guarantees and Maximum Recovery [Line Items]
Contractual terms of our guarantees	30 days		30 days	30 days		30 days
Maximum [Member]
Financial Guarantees and Maximum Recovery [Line Items]
Contractual terms of our guarantees	40 years		40 years	40 years		40 years
Current Debt Service Coverage Ratio, Higher Risk Loans1				1.0			1.0

[1] Primarily consists of the unpaid principal balance of the underlying mortgage loans.

[2] Recoverability of such credit enhancements and recourse is subject to, among other factors, our mortgage insurers’ and financial guarantors’ ability to meet their obligations to us. For information on our mortgage insurers, see “Note 14, Concentrations of Credit Risk.”

[3] Primarily consists of credit enhancements, long-term standby commitments, and our commitment under the TCLF program.