Debt (Fair Value Of Fixed Rate Notes) (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2012
Seven Hundred Fifty Million Fixed Rate Notes Due August Two Thousand Thirteen, Interest Equal To Five Point Four Zero Percent [Member]
Debt Instrument [Line Items]
Debt instrument, fair value	$ 781.8
Debt instrument, face amount	750.0
Debt instrument, maturity date	Aug. 01, 2013
$750.0 million fixed rate notes due February 2014, interest equal to 5.75% [Member]
Debt Instrument [Line Items]
Debt instrument, fair value	803.7
Debt instrument, face amount	750.0
Debt instrument, maturity date	Feb. 01, 2014
$612.5 million fixed rate notes due March 2018, interest equal to 4.40% [Member]
Debt Instrument [Line Items]
Debt instrument, fair value	690.6
Debt instrument, face amount	612.5
Debt instrument, maturity date	Mar. 01, 2018
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]
Debt instrument, fair value	759.4
Debt instrument, face amount	$ 750.0
Debt instrument, maturity date	Sep. 01, 2022