Earnings Per Share (Tables)

9 Months Ended

Sep. 30, 2017

Earnings Per Share [Abstract]

Computation of Basic and Diluted Earnings per Share

	Three Months Ended				Nine Months Ended
	September 30,				September 30,
(in millions, except per share data)	2017		2016		2017		2016
Net income attributable to common shareholders	$	68.2	$	63.5	$	200.5	$	186.8
Average basic shares outstanding	59.5		58.5		59.4		58.3
Effect of dilutive stock options	0.9		0.9		1.0		0.9
Average diluted shares outstanding	60.4		59.4		60.4		59.2
Earnings per basic share	$	1.15	$	1.09	$	3.38	$	3.20
Earnings per diluted share	$	1.13	$	1.07	$	3.32	$	3.16