Share-Based Compensation (Summary Of Share Options Outstanding And Exercisable) (Details) (USD $) In Millions, except Share data, unless otherwise specified				3 Months Ended
	Mar. 31, 2012		Dec. 31, 2011	Mar. 31, 2012 $30.06-$41.16 [Member]		Mar. 31, 2012 $42.90-$45.53 [Member]		Mar. 31, 2012 $48.02-$73.32 [Member]
Range of exercise prices, minimum				$ 30.06		$ 42.90		$ 48.02
Range of exercise prices, maximum				$ 41.16		$ 45.53		$ 73.32
Outstanding Options, Number	1,129,156	[1]	1,339,536	414,656	[1]	466,060	[1]	248,440	[1]
Outstanding Options, Weighted Average Price	$ 41.61	[1]	$ 42.27	$ 32.06	[1]	$ 44.32	[1]	$ 52.43	[1]
Exercisable Options, Number	841,612	[1]		218,853	[1]	447,429	[1]	175,330	[1]
Exercisable Options, Weighted Average Price	$ 43.68	[1]		$ 33.86	[1]	$ 44.34	[1]	$ 54.27	[1]
Aggregate intrinsic value of outstanding options	$ 27.4
Aggregate Intrinsic Value of Exercisable Options	$ 18.7
Closing share price per share for calculation of aggregate intrinsic values	$ 65.75

[1] The aggregate intrinsic value of outstanding and exercisable options at March 31, 2012 were $27.4 million and $18.7 million, respectively. The aggregate intrinsic values were calculated as the excess, if any, between our closing share price of $65.75 per share on March 31, 2012 and the strike price of the underlying award.