Earnings Per Share - Basic and Diluted Loss Per Share (Detail) - shares shares in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Earnings Per Share [Abstract]
Weighted average common shares outstanding	89.8	91.5	90.9
Add: Weighted average restricted stock awards outstanding(a)	0.0	0.0	0.1	[1]
Basic weighted average common shares outstanding	89.8	91.5	91.0
Add: Dilutive impact of outstanding equity awards	0.9	1.3	1.3
Diluted weighted average common shares outstanding	90.7	92.8	92.3

[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.