Debt (Components of Notes Payable) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Short-term Debt [Line Items]
Principal amount	$ 739	$ 234	[1]
Euro Commercial Paper [Member]
Short-term Debt [Line Items]
Principal amount	464	0
Effective interest rate	0.64%	0.00%
U.S. Commercial Paper [Member]
Short-term Debt [Line Items]
Principal amount	245	216
Effective interest rate	0.26%	0.24%
Bank Borrowings [Member]
Short-term Debt [Line Items]
Principal amount	$ 30	$ 18

[1] * Condensed from audited financial statements.