Variable Interest Entities - Resecuritizations, Multi-seller Conduits (Details 1) (USD $)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Variable Interest Entity
Securities transferred to agency resecuritization VIEs	$ 4,200,000,000	$ 2,900,000,000
Securities transferred to private-label re-securitization VIEs	0	241,000,000
Assets	2,389,349,000,000	2,320,164,000,000	2,359,141,000,000
Unfunded Portion of Commitments to Multi-Seller Conduits	1,033,610,000,000	997,503,000,000	1,027,988,000,000
Mortgage Securitization Entities | Re securitizations
Variable Interest Entity
Senior and subordinated interest in nonconsolidated agency re-securitization entities	1,700,000,000		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	21,000,000		61,000,000
Mortgage Securitization Entities | Re securitizations | Residential mortgage | Private label Resecuritizations
Variable Interest Entity
Variable Interest Entity, Consolidated, Carrying Amount, Assets	83,000,000		76,000,000
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	2,000,000		5,000,000
Multi-seller conduits
Variable Interest Entity
Commercial paper issued by consolidated Variable Interest Entities eliminated in Consolidation	3,800,000,000		8,300,000,000
Multi-seller conduits | Commercial Mortgage Backed Securities
Variable Interest Entity
Unfunded Portion of Commitments to Multi-Seller Conduits	10,900,000,000		10,800,000,000
Nonconsolidated Private-Label Re-securitizations
Variable Interest Entity
Assets	$ 3,900,000,000		$ 4,600,000,000