Changes in Number of Shares of Common Stock Outstanding (Detail) - shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Beginning balance (in shares)	229,293,783	233,390,705	237,322,035
Incentive Plan and Awards (in shares)	1,209,124	1,033,664	1,040,015
Stock Options Exercised (in shares)	4,156,728	1,721,282	2,515,769
Treasury Stock Purchased (in shares)	(6,054,150)	(6,851,868)	(7,487,114)
Ending balance (in shares)	228,605,485	229,293,783	233,390,705