Capital Stock, Dividends and Common Stock Repurchase Program (ASR) (Detail) $ / shares in Units, shares in Thousands, $ in Millions	1 Months Ended		12 Months Ended
	Feb. 28, 2017 $ / shares shares	Nov. 30, 2016 USD ($) shares	Dec. 31, 2017 USD ($) item $ / shares shares	Dec. 31, 2016 USD ($) item $ / shares shares	Dec. 31, 2015 USD ($) item $ / shares shares	Dec. 01, 2017 USD ($)
Accelerated Share Repurchases [Line Items]
Shares repurchased | shares			10,058	11,241	14,823
Weighted average per share purchase price | $ / shares			$ 77.67	$ 60.49	$ 49.83
Total repurchases			$ 750	$ 725	$ 600
Cash paid for repurchase of common stock			$ 750	$ 725	$ 600
Accelerated Share Repurchase Agreement (ASR) [Member]
Accelerated Share Repurchases [Line Items]
Shares repurchased | shares	3,200	400			2,800
Weighted average per share purchase price | $ / shares	$ 69.43
Total repurchases		$ 225
Number of ASR agreements | item			2	4	2
Cash paid for repurchase of common stock			$ 750	$ 725	$ 600
Authorized share repurchases						$ 1,250