Shareholders' Equity (Common Stock Issued With The Exercise Of Stock Options) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Stockholders' Equity Note [Abstract]
Shares issued (in shares)	0.3	0.6
Proceeds from the exercise of stock options	$ 13.3	$ 21.5
Average exercise price per share (in dollars per share)	$ 51.15	$ 34.03