Earnings Per Share (Tables)

3 Months Ended

Mar. 31, 2018

Earnings Per Share [Abstract]

Computation of Basic and Diluted Earnings per Share

	Three Months Ended
	March 31,
(in millions, except per share data)	2018		2017
Net income attributable to common shareholders	$	68.7	$	63.1
Average basic shares outstanding	59.7		59.3
Effect of dilutive stock options	1.3		1.0
Average diluted shares outstanding	61.0		60.3
Earnings per basic share	$	1.15	$	1.06
Earnings per diluted share	$	1.13	$	1.05