Shareholders' Equity (Shares Repurchased Under Share Repurchase Program) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Class of Stock [Line Items]
Aggregate purchase price	$ 371.1
Treasury Stock [Member]
Class of Stock [Line Items]
Aggregate purchase price	371.1
Stock Repurchase Program Board Authorized Repurchases [Member]
Class of Stock [Line Items]
Stock Repurchase Program, Authorized Amount	$ 250.0
Shares repurchased (in shares)	7.9	0.2
Aggregate purchase price	$ 370.6	$ 9.1
Average purchase price per share (in dollars per share)	$ 47.20	$ 60.46
Remaining amount available for share repurchase	$ 175.0