Shareholders' Equity (Shares Repurchased Under Share Repurchase Program) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Class of Stock [Line Items]
Aggregate purchase price	$ 80.0	$ 33.5
Stock Repurchase Program Board Authorized Repurchases [Member]
Class of Stock [Line Items]
Shares repurchased (in shares)	2.5	1.0
Aggregate purchase price	$ 80.0	$ 33.5
Average purchase price per share (in dollars per share)	$ 31.95	$ 34.34
Remaining amount available for share repurchase	$ 139.0