Shareholders' Equity (Shares Repurchased Under Share Repurchase Program) (Details) (USD $) In Millions, except Per Share data	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Stockholders' Equity Note [Abstract]
Shares repurchased	5.7	2.9	10.8	25.9
Aggregate purchase price	$ 195.9	$ 55.0	$ 365.6	$ 506.6
Average purchase price per share	$ 34.66	$ 19.08	$ 33.85	$ 19.59