Debt (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		3 Months Ended	6 Months Ended
	Jun. 30, 2012	Jul. 31, 2012 Interest Rate Contract [Member] Forward Swap [Member] New Contract [Member]	Jun. 30, 2012 Debt Due 2012 [Member]	Jun. 30, 2012 Debt Due 2012 [Member]	Jun. 30, 2012 Term Loan Due 2012 [Member]	Jun. 30, 2012 Maximum [Member]	Jun. 30, 2012 Average Borrowings [Member]
Debt Instrument [Line Items]
Extinguishment of Debt, Amount				$ 400	$ 150
Debt Instrument, Interest Rate, Stated Percentage			4.625%	4.625%
Commercial Paper						343	142
Short-term Debt, Weighted Average Interest Rate	0.38%
Notional Amount Of Derivatives		150
Derivative, Loss on Derivative	6
Extinguishment of Debt, Gain (Loss), Net of Tax			$ 2