Debt (Schedule Of Short-Term And Long-Term Debt) (Details) (USD $) In Millions, unless otherwise specified	1 Months Ended			9 Months Ended		9 Months Ended		9 Months Ended		9 Months Ended
	Sep. 30, 2012	Feb. 28, 2010	Dec. 31, 2011	Sep. 30, 2012 Seven Hundred Fifty Million Fixed Rate Notes Due August Two Thousand Thirteen, Interest Equal To Five Point Four Zero Percent [Member]	Dec. 31, 2011 Seven Hundred Fifty Million Fixed Rate Notes Due August Two Thousand Thirteen, Interest Equal To Five Point Four Zero Percent [Member]	Sep. 30, 2012 $750.0 million fixed rate notes due February 2014, interest equal to 5.75% [Member]	Dec. 31, 2011 $750.0 million fixed rate notes due February 2014, interest equal to 5.75% [Member]	Sep. 30, 2012 $612.5 million fixed rate notes due March 2018, interest equal to 4.40% [Member]	Dec. 31, 2011 $612.5 million fixed rate notes due March 2018, interest equal to 4.40% [Member]	Sep. 30, 2012 Seven Hundred Fifty Million Fixed Rate Notes Due March Two Thousand Twenty Two, Interest Equal To Three Point Zero Percent [Member] [Member]	Dec. 31, 2011 Seven Hundred Fifty Million Fixed Rate Notes Due March Two Thousand Twenty Two, Interest Equal To Three Point Zero Percent [Member] [Member]
Debt Instrument [Line Items]
Long-term debt	$ 2,106.4		$ 2,106.8	$ 0	$ 749.2	$ 748.7	$ 748.0	$ 610.0	$ 609.6	$ 747.7	$ 0
Forward starting interest rate swap agreement fixed rate	3.32%	4.46%
Debt instrument, face amount				$ 750.0		$ 750.0		$ 612.5		$ 750.0
Debt instrument, maturity date				Aug. 01, 2013		Feb. 01, 2014		Mar. 01, 2018		Sep. 01, 2022
Debt Instrument, Interest Rate, Stated Percentage				5.40%		5.75%		4.40%		3.00%