Shareholders' Equity (Narrative) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	6 Months Ended		3 Months Ended		6 Months Ended		1 Months Ended
	Jun. 30, 2012	Jun. 30, 2012 Treasury Stock [Member]	Jun. 30, 2012 Stock Repurchase Program Board Authorized Repurchases [Member]	Jun. 30, 2011 Stock Repurchase Program Board Authorized Repurchases [Member]	Jun. 30, 2012 Stock Repurchase Program Board Authorized Repurchases [Member]	Jun. 30, 2011 Stock Repurchase Program Board Authorized Repurchases [Member]	Jul. 18, 2012 Stock Repurchase Program Board Authorized Repurchases [Member] Repurchase of Equity [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					118.2		368.2
Shares repurchased			3.7	3.4	15.4	5.1
Aggregate purchase price	$ 532.9	$ 532.9	$ 126.2	$ 110.9	$ 531.6	$ 169.7
Average purchase price per share			$ 33.99	$ 33.04	$ 34.54	$ 32.97