Stock-Based Compensation - Summary of Options Outstanding (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise Prices, Minimum (in dollars per share)	$ 29.59
Range of Exercise Prices, Maximum (in dollars per share)	$ 77.26
Options Outstanding, Number Outstanding (in shares)	6,753,801	6,973,591	7,734,841	7,889,321
Options Outstanding, Weighted- Average Remaining Contractual Life (Years)	4 years 10 months 21 days	4 years 8 months 12 days
Options Outstanding, Weighted- Average Exercise Price (in dollars per share)	$ 53.59	$ 44.64	$ 38.84	$ 32.91
Options Exercisable, Number Exercisable (in shares)	2,928,979	3,115,847	3,774,061
Options Exercisable, Weighted- Average Exercise Price (in dollars per share)	$ 43.79	$ 36.81	$ 29.37
$29.59 - $37.40
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise Prices, Minimum (in dollars per share)	29.59
Range of Exercise Prices, Maximum (in dollars per share)	$ 37.4
Options Outstanding, Number Outstanding (in shares)	1,421,268
Options Outstanding, Weighted- Average Remaining Contractual Life (Years)	2 years 2 months 12 days
Options Outstanding, Weighted- Average Exercise Price (in dollars per share)	$ 34.54
Options Exercisable, Number Exercisable (in shares)	1,366,689
Options Exercisable, Weighted- Average Exercise Price (in dollars per share)	$ 34.42
50.64
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise Prices, Minimum (in dollars per share)	50.64
Range of Exercise Prices, Maximum (in dollars per share)	$ 50.64
Options Outstanding, Number Outstanding (in shares)	1,405,725
Options Outstanding, Weighted- Average Remaining Contractual Life (Years)	6 years 4 months 21 days
Options Outstanding, Weighted- Average Exercise Price (in dollars per share)	$ 50.64
Options Exercisable, Number Exercisable (in shares)	0
Options Exercisable, Weighted- Average Exercise Price (in dollars per share)	$ 0.00
50.69 - 51.62
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise Prices, Minimum (in dollars per share)	50.69
Range of Exercise Prices, Maximum (in dollars per share)	$ 51.62
Options Outstanding, Number Outstanding (in shares)	1,090,703
Options Outstanding, Weighted- Average Remaining Contractual Life (Years)	3 years 8 months 9 days
Options Outstanding, Weighted- Average Exercise Price (in dollars per share)	$ 50.70
Options Exercisable, Number Exercisable (in shares)	958,463
Options Exercisable, Weighted- Average Exercise Price (in dollars per share)	$ 50.70
53.61 - 56.32
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise Prices, Minimum (in dollars per share)	53.61
Range of Exercise Prices, Maximum (in dollars per share)	$ 56.32
Options Outstanding, Number Outstanding (in shares)	1,384,582
Options Outstanding, Weighted- Average Remaining Contractual Life (Years)	4 years 7 months 17 days
Options Outstanding, Weighted- Average Exercise Price (in dollars per share)	$ 53.65
Options Exercisable, Number Exercisable (in shares)	594,184
Options Exercisable, Weighted- Average Exercise Price (in dollars per share)	$ 53.71
73.92 - 77.26
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise Prices, Minimum (in dollars per share)	73.92
Range of Exercise Prices, Maximum (in dollars per share)	$ 77.26
Options Outstanding, Number Outstanding (in shares)	1,451,523
Options Outstanding, Weighted- Average Remaining Contractual Life (Years)	7 years 2 months 23 days
Options Outstanding, Weighted- Average Exercise Price (in dollars per share)	$ 77.24
Options Exercisable, Number Exercisable (in shares)	9,643
Options Exercisable, Weighted- Average Exercise Price (in dollars per share)	$ 73.92