Earnings Per Share Computations (Tables)

12 Months Ended

Dec. 31, 2017

Earnings Per Share [Abstract]

Calculation of earnings per share

A reconciliation of basic and diluted earnings per share is below: 

(in millions, except per share amounts)	2017		2016		2015
Numerator
Net income	$	94.0	$	236.2	$	239.3
Denominator
Weighted-average common shares outstanding — basic	91.5		94.3		96.7
Dilutive shares	0.4		0.8		1.2
Weighted-average common and common equivalent shares outstanding — diluted	91.9		95.1		97.9
Per common share income
Basic	$	1.03	$	2.51	$	2.47
Diluted	$	1.02	$	2.48	$	2.44