Stock-Based Compensation - Schedule of Stock Option Plans Activity (Detail) $ / shares in Units, shares in Thousands, $ in Thousands	6 Months Ended
	Jun. 30, 2018 USD ($) $ / shares shares
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Outstanding at beginning of year, Shares | shares	4,106
Granted, Shares | shares	265
Exercised, Shares | shares	(288)
Canceled, Shares | shares	0
Outstanding at end of year, Shares | shares	4,083
Stock Options exercisable at end of year, Shares | shares	2,368
Outstanding at beginning of year, Weighted - Average Exercise Price | $ / shares	$ 47.96
Granted, Weighted - Average Exercise Price | $ / shares	65.80
Exercised, Weighted - Average Exercise Price | $ / shares	42.64
Canceled, Weighted - Average Exercise Price | $ / shares	0
Outstanding at end of period, Weighted - Average Exercise Price | $ / shares	49.49
Stock options exercisable at end of year, Weighted - Average Exercise Price | $ / shares	$ 45.50
Outstanding at end of period, Weighted - Average Remaining Contractual Life	6 years 9 months 18 days
Stock options exercisable at end of period, Weighted - Average Remaining Contractual Life	5 years 7 months 6 days
Exercised, Aggregate Intrinsic Value | $	$ 7,253
Outstanding at end of period, Aggregate Intrinsic Value | $	53,997
Stock options exercisable at end of period, Aggregate Intrinsic Value | $	$ 40,350