Reconciliation of Basic to Diluted Shares Outstanding (Detail) - shares shares in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Schedule Of Earnings Per Share Basic And Diluted By Common Class [Line Items]
Basic	191.7	199.4	193.3	201.1
Dilutive effect of shares issuable under stock-based compensation plans	2.6	3.1	2.7	3.4
Diluted	194.3	202.5	196.0	204.5
Anti-dilutive options to purchase common shares and restricted stock as well as contingently issuable restricted stock which are excluded from the table above	0.5	0.6	0.9	0.8