Shareholders' Equity (Shares Repurchased Under Share Repurchase Program) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended					9 Months Ended
	Sep. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019	Oct. 19, 2020
Class of Stock [Line Items]
Aggregate purchase price		$ 80.0		$ 11.2	$ 33.5
Stock Repurchase Program Board Authorized Repurchases [Member]
Class of Stock [Line Items]
Shares repurchased (in shares)	0.0		0.0			2.5	1.3
Aggregate purchase price	$ 0.0		$ 0.0			$ 80.0	$ 44.7
Average purchase price per share (in dollars per share)	$ 0		$ 0			$ 31.95	$ 35.51
Stock Repurchase Program Board Authorized Repurchases [Member] | Subsequent Event [Member]
Class of Stock [Line Items]
Remaining amount available for share repurchase								$ 500.0