Commitments and Guarantees (Repurchase Agreement By Type Of Collateral Pledged) (Details) - Overnight or Continuous [Member] $ in Millions	Sep. 30, 2015 USD ($)
Transfer Of Certain Financial Assets Accounted For As Secured Borrowings [Line Items]
Gross Repurchase Agreements	$ 2,003
US Treasury and Government Agency Securities [Member]
Transfer Of Certain Financial Assets Accounted For As Secured Borrowings [Line Items]
Gross Repurchase Agreements	88
Residential mortgage-backed Securities [Member] | Mortgage-backed Securities Agency [Member]
Transfer Of Certain Financial Assets Accounted For As Secured Borrowings [Line Items]
Gross Repurchase Agreements	1,847
Commercial mortgage-backed securities [Member] | Mortgage-backed Securities Agency [Member]
Transfer Of Certain Financial Assets Accounted For As Secured Borrowings [Line Items]
Gross Repurchase Agreements	$ 68