Shareholders' Equity (Narrative) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Class of Stock [Line Items]
Aggregate purchase price			$ 533.2
Treasury Stock [Member]
Class of Stock [Line Items]
Aggregate purchase price			533.2
Stock Repurchase Program Board Authorized Repurchases [Member]
Class of Stock [Line Items]
Additional authorized amount for share repurchases under the share repurchase program	250.0
Amount available for share repurchases under the share repurchase program			368.2
Shares repurchased	0	5.7	15.4	10.8
Aggregate purchase price	$ 0	$ 195.9	$ 531.6	$ 365.6
Average purchase price per share	$ 0.00	$ 34.66	$ 34.54	$ 33.85