Share-Based Compensation - Summary of Stock Option Activity (Detail) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($) $ / shares shares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Outstanding stock options, Beginning balance | shares	7,901
Options granted | shares	1,663
Options exercised | shares	(1,730)
Options forfeited | shares	(532)
Options expired | shares	(45)
Outstanding stock options, Ending Balance | shares	7,257
Number of outstanding options, Vested or expected to vest | shares	6,742
Exercisable, Stock options | shares	4,107
Outstanding Weighted average exercise price, Beginning Balance | $ / shares	$ 86.21
Options granted, Weighted average exercise price | $ / shares	121.52
Options exercised, Weighted average exercise price | $ / shares	79.41
Options forfeited, Weighted average exercise price | $ / shares	113.54
Options expired, Weighted average exercise price | $ / shares	96.27
Outstanding Weighted average exercise price, ending Balance | $ / shares	93.83
Outstanding Weighted average exercise price, Vested or expected to vest | $ / shares	92.36
Exercisable, Weighted average exercise price | $ / shares	$ 79.67
Weighted Average Remaining Contractual Life, Outstanding at December 31, 2017	6 years 3 months 18 days
Weighted Average Remaining Contractual Life, Vested or expected to vest as of December 31, 2017	6 years 2 months 12 days
Weighted Average Remaining Contractual Life, Exercisable at December 31, 2017	4 years 7 months 6 days
Intrinsic Value, Outstanding at December 31, 2017 | $	$ 197.0
Intrinsic Value, Vested or expected to vest as of December 31, 2017 | $	192.8
Intrinsic Value, Exercisable at December 31, 2017 | $	$ 168.6