Share-based Compensation - Schedule of Stock Option Plans (Detail)	12 Months Ended
	Dec. 31, 2017 $ / shares shares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Outstanding at the beginning of the period (in shares) | shares	1,137,179
Granted | shares	165,595
Exercised | shares	(152,027)
Forfeited | shares	(63,925)
Outstanding at the end of the period (in shares) | shares	1,086,822
Vested and expected to vest | shares	1,086,822
Exercisable (in shares) | shares	608,320
Outstanding at the beginning of the period (in dollars per share) | $ / shares	$ 36.05
Granted | $ / shares	46.10
Exercised | $ / shares	34.14
Forfeited | $ / shares	42.50
Outstanding at the end of the period (in dollars per share) | $ / shares	37.47
Vested and expected to vest | $ / shares	37.47
Exercisable | $ / shares	$ 34.33
Options outstanding, weighted average remaining contractual term	7 years 21 days
Options vested and expected, weighted average remaining contractual term	7 years 21 days
Options exercisable, weighted average remaining contractual term	5 years 11 months 8 days