Net Income Per Share (Tables)

9 Months Ended

Sep. 30, 2013

Earnings Per Share [Abstract]

Net income and shares used in basic and diluted net income per share

The following table reconciles net income and shares used in the calculation of basic net income per share to those used for diluted net income per share:

	Three Months Ended September 30,				Nine Months Ended September 30,
($ in millions)	2013		2012		2013		2012
Net income, as reported, for basic net income per share	$	26.8	$	14.8	$	88.7	$	59.6
Plus: interest expense on convertible debt, net of tax	—		—		—		1.9
Net income for diluted net income per share	$	26.8	$	14.8	$	88.7	$	61.5
Weighted average common shares outstanding	69.8		68.3		69.4		68.0
Dilutive effect of stock options, stock appreciation rights and performance share awards, based on the treasury stock method	1.6		1.0		1.4		0.9
Assumed conversion of convertible debt, based on the if-converted method	—		0.1		0.1		3.4
Weighted average shares assuming dilution	71.4		69.4		70.9		72.3