Shareholders' Equity Shareholders' Equity (Common Stock Issued With The Exercise Of Stock Options (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Stockholders' Equity Note [Abstract]
Shares issued (in shares)	0.5	1.0	0.3
Proceeds from the exercise of stock options	$ 17.8	$ 39.7	$ 8.4
Average exercise price per share (in dollars per share)	$ 35.25	$ 37.85	$ 31.21