Earnings Per Share (Tables)

3 Months Ended

Mar. 31, 2013

Earnings Per Share [Abstract]

Calculation of basic and diluted earnings per share

Basic and diluted earnings per share were calculated as follows, for each period presented:

	Quarter Ended
	March 31,
	2013		2012
Numerator:
Net income	$	33.5	$	26.5
Denominator — Weighted-average common shares outstanding (in thousands)1:
Basic	19,143		19,059
Diluted	19,366		19,161
Earnings per common share, Basic:
Net income per share	$	1.75	$	1.39
Earnings per common share, Diluted:
Net income per share	$	1.73	$	1.38

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¹  The basic weighted-average number of common shares outstanding during the period excludes unvested share-based payment awards. The diluted weighted-average number of common shares outstanding during the period is calculated using the treasury method.