Financial Guarantees and Maximum Recovery (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
Financial Guarantees and Maximum Recovery [Line Items]
Maximum Exposure	$ 32,339	$ 35,965
Guaranty Obligation	338	382
Maximum Recovery	12,048	14,222
Fair Value of guaranty obligations in Investments in Securities	729	797
Unconsolidated VIEs [Member] | Unconsolidated Fannie Mae MBS [Member]
Financial Guarantees and Maximum Recovery [Line Items]
Maximum Exposure	15,556	17,184
Guaranty Obligation	198	214
Maximum Recovery	9,077	9,775
Unconsolidated VIEs [Member] | Other guaranty arrangements [Member]
Financial Guarantees and Maximum Recovery [Line Items]
Maximum Exposure	16,783	18,781
Guaranty Obligation	140	168
Maximum Recovery	$ 2,971	$ 4,447
Minimum [Member]
Financial Guarantees and Maximum Recovery [Line Items]
Remaining contractual terms of our guarantees	1 day
Maximum [Member]
Financial Guarantees and Maximum Recovery [Line Items]
Remaining contractual terms of our guarantees	37 years