Reconciliation of Basic to Diluted Shares Outstanding (Detail) - shares shares in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Schedule Of Earnings Per Share Basic And Diluted By Common Class [Line Items]
Basic	199.4	210.4	201.1	212.1
Dilutive effect of shares issuable under stock-based compensation plans	3.1	3.8	3.4	4.0
Diluted	202.5	214.2	204.5	216.1
Anti-dilutive options to purchase common shares and restricted stock as well as contingently issuable restricted stock which are excluded from the table above	0.6	0.5	0.8	0.7