Commitments and Guarantees (Resale and Repurchase Agreements) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Offsetting Assets [Line Items]
Gross Resale Agreements	$ 1,089	$ 975
Net Resale Agreements	1,089	975
Securities Collateral Held Under Master Netting Agreements	999	884
Net Amounts	90	91
Offsetting Liabilities [Line Items]
Gross Repurchase Agreements	3,237	3,215
Net Repurchase Agreements	3,237	3,215
Securities Collateral Pledged Under Master Netting Agreements	2,355	2,168
Net Amounts	882	1,047
Municipalities, Pension plans and Certain trusts and insurance companies [Member]
Offsetting Liabilities [Line Items]
Net Repurchase Agreements	832	997
Long Term Repurchase Agreements [Member]
Offsetting Liabilities [Line Items]
Net Repurchase Agreements	50	50
Accrued Interest Income [Member]
Offsetting Assets [Line Items]
Net Resale Agreements	1	1
Long Term Resale Agreements [Member]
Offsetting Assets [Line Items]
Net Resale Agreements	$ 89	$ 89