Computation of Weighted Average 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
Earnings Per Share Disclosure [Line Items]
Basic	200.1	184.3	190.6	185.6
Dilutive share-based awards	0.2	0.3	0.3	0.7
Convertible debt	9.0	3.1	8.6	3.2
Diluted	209.3	187.7	199.5	189.5