Changes in Number of Shares of Common Stock Outstanding (Detail) - shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Beginning balance (in shares)	233,390,705	237,322,035	238,914,988
Incentive Plan and Awards (in shares)	1,033,664	1,040,015	863,958
Stock Options Exercised (in shares)	1,721,282	2,515,769	3,088,490
Treasury Stock Purchased (in shares)	(6,851,868)	(7,487,114)	(5,545,401)
Ending balance (in shares)	229,293,783	233,390,705	237,322,035