Earnings Per Share - Basic and Diluted Loss Per Share (Detail) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013		Dec. 31, 2012
Earnings Per Share [Abstract]
Weighted average common shares outstanding	91.5	90.9		92.7
Add: Weighted average restricted stock awards outstanding(a)	0	0.1	[1]	0.3	[1]
Basic weighted average common shares outstanding	91.5	91.0		93.0
Add: Dilutive impact of stock options and restricted stock units	1.3	1.3		1.1
Diluted weighted average common shares outstanding	92.8	92.3		94.1

[1] (a)Restricted stock awards containing rights to non-forfeitable dividends which participate in undistributed earnings with common shareholders are considered participating securities for purposes of computing earnings per share.