Changes in Number of Shares of Common Stock Outstanding (Detail)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Reconciliation of Common Stock Outstanding [Line Items]
Beginning balance	237,322,035	238,914,988	241,008,509
Incentive Plan and Awards	1,040,015	863,958	449,463
Stock Options Exercised	2,515,769	3,088,490	973,270
Treasury Stock Purchased	(7,487,114)	(5,545,401)	(3,516,254)
Ending balance	233,390,705	237,322,035	238,914,988