Derivatives (Details 2) (Not designated as hedging instruments, USD $) In Millions, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Derivatives
Asset	$ 173	$ 235
Liability	24	132
Forward delivery commitments subject to master netting arrangements
Derivatives
Asset	25	32
Liability	12	100
Forward delivery commitments subject to master netting arrangements | Other Assets
Derivatives
Asset	23
Liability	10
Forward delivery commitments subject to master netting arrangements | Other Liabilities
Derivatives
Asset	2	32
Liability	$ 2	$ 100