Reconciliation of Basic to Diluted Shares Outstanding (Detail) - shares shares in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Schedule Of Weighted Average Number Of Diluted Shares Outstanding [Line Items]
Basic	200.1	210.7	219.4
Dilutive effect of shares issuable under stock-based compensation plans	3.3	4.0	4.1
Diluted	203.4	214.7	223.5
Antidilutive options to purchase common shares and restricted stock as well as contingently issuable restricted stock which are excluded from the table above	0.7	0.7	4.0