Net Income Per Share(Tables)

6 Months Ended

Jun. 30, 2014

Net Income Per Share [Abstract]

Reconciliation of the Common and Potential Common Shares Outstanding Used in Earnings Per Share Calculation

A reconciliation of the average number of common and potential common shares outstanding used in the calculations of basic and diluted net income per share follows ($ in millions, shares in thousands):

	Three Months Ended						Six Months Ended
	June 30, 2014			June 30, 2013			June 30, 2014			June 30, 2013
Numerator (basic and diluted):
Net income	$	25.0		$	26.6		$	48.2		$	56.7
Less: Dividends paid to participating securities	(0.1		)	—			(0.2		)	(0.1		)
Less: Undistributed earnings available to participating securities	(0.2		)	(0.2		)	(0.3		)	(0.4		)
Undistributed and distributed earnings available to common stockholders	$	24.7		$	26.4		$	47.7		$	56.2
Denominator:
Average number of common shares outstanding	30,096.5			31,097.3			30,379.7			31,021.9
Effect of dilutive stock-based compensation	114.2			162.2			113.2			162.7
Average number of common and potential common shares outstanding	30,210.7			31,259.5			30,492.9			31,184.6