Variable Interest Entities - Resecuritizations, Multi-seller Conduits (Details 1) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Variable Interest Entity
Securities transferred to agency resecuritization VIEs	$ 2,900,000,000	$ 3,100,000,000	$ 7,100,000,000	$ 6,000,000,000
Securities transferred to private-label re-securitization VIEs	0	0	0	241,000,000
Total assets	2,439,494,000,000	2,290,146,000,000	2,439,494,000,000	2,290,146,000,000	2,359,141,000,000
Unfunded Portion of Commitments to Multi-Seller Conduits	1,040,134,000,000	1,016,346,000,000	1,040,134,000,000	1,016,346,000,000	1,027,988,000,000
Mortgage Securitization Entities | Re securitizations
Variable Interest Entity
Senior and subordinated interest in nonconsolidated agency re-securitization entities	2,400,000,000		2,400,000,000		2,000,000,000
Mortgage Securitization Entities | Re securitizations | Private label Resecuritizations
Variable Interest Entity
Senior and subordinated interest in nonconsolidated agency re-securitization entities	5,000,000		5,000,000		61,000,000
Mortgage Securitization Entities | Re securitizations | Residential mortgage | Private label Resecuritizations
Variable Interest Entity
Variable Interest Entity, Consolidated, Carrying Amount, Assets	88,000,000		88,000,000		76,000,000
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	3,000,000		3,000,000		5,000,000
Multi-seller conduits
Variable Interest Entity
Commercial paper issued by consolidated Variable Interest Entities eliminated in Consolidation	3,800,000,000		3,800,000,000		8,300,000,000
Multi-seller conduits | Commercial Mortgage Backed Securities
Variable Interest Entity
Unfunded Portion of Commitments to Multi-Seller Conduits	12,100,000,000		12,100,000,000		10,800,000,000
Nonconsolidated Private-Label Re-securitizations
Variable Interest Entity
Total assets	$ 3,800,000,000		$ 3,800,000,000		$ 4,600,000,000