Schedule of Actual Weighted Average Shares Used in Calculating Earnings Per Share (Detail) - shares shares in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Schedule of Weighted Average Number of Diluted Shares Outstanding [Line Items]
Weighted average shares basic	88.0	93.2	88.2	93.6
Effect of dilutive securities:
stock options/share awards	0.3	0.3	0.2	0.3
Weighted average shares diluted	88.3	93.5	88.4	93.9