Earnings per Share (Tables)

3 Months Ended

Mar. 31, 2018

Earnings Per Share [Abstract]

Summary of Earnings Per Share

Per share amounts are computed as follows:

	Three Months Ended March 31
	2018		2017
Numerator (in millions):
Net income available to common stockholders	$	22.2	$	17.2
Denominator (in thousands):
Weighted average common shares outstanding		24,369		24,087
Dilutive effect of stock options and awards		205		440
Denominator for diluted earnings per share		24,574		24,527
Net income per share, basic:	$	0.91	$	0.71
Net income per share, diluted:	$	0.90	$	0.70