Net Income Per Share and Stockholders' Equity (Tables)

3 Months Ended

Mar. 31, 2018

Earnings Per Share [Abstract]

Calculation of basic and diluted earnings per share

basic and diluted net income per share for periods presented (in millions of dollars, except share and per share amounts):

	Quarter Ended
	March 31,
	2018		2017
Numerator:
Net income	$	25.7	$	36.0
Denominator – Weighted-average common shares outstanding (in thousands):
Basic	16,707		17,385
Add: dilutive effect of non-vested common shares, restricted stock units and performance shares	324		218
Diluted	17,031		17,603
Net income per common share, Basic:	$	1.54	$	2.07
Net income per common share, Diluted:	$	1.51	$	2.04

Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share

The following securities were excluded from the weighted-average diluted shares computation for the periods presented as their inclusion would have been anti-dilutive (in thousands of shares):

	Quarter Ended
	March 31,
	2018	2017
Options to purchase common shares1	—	2
Non-vested common shares, restricted stock units and performance shares	—	64
Total excluded	—	64

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¹  Related to the 1,543 fully-vested stock options that were outstanding as of March 31, 2017 and subsequently expired on April 2, 2017.