Stock-Based Compensation (Stock Options Outstanding, Exercisable and Activity) (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Number of Shares
Beginning Balance	3,575,625
Granted	533,105
Exercised	(288,760)
Forfeited/Expired	(58,970)
Ending Balance	3,761,000	3,575,625
Vested or expected to vest, at end of period	3,724,235
Exercisable, at end of period	1,924,079
Weighted Average Exercise Price
Beginning Balance (in dollars per share)	$ 83.34
Granted (in dollars per share)	115.98
Exercised (in dollars per share)	50.82
Forfeited/Expired (in dollars per share)	106.32
Ending Balance (in dollars per share)	90.10	$ 83.34
Vested or expected to vest, at end of period (in dollars per share)	89.89
Exercisable, at end of period (in dollars per share)	$ 77.79
Weighted Average Remaining Contractual Life (in years)
Outstanding	6 years 1 month	6 years 5 months
Vested or expected to vest, at end of period	6 years 1 month
Exercisable, at end of period	4 years 3 months
Intrinsic Value (in millions)
Outstanding	$ 61	$ 120
Vested or expected to vest, at end of period	61
Exercisable, at end of period	$ 56