Stock-based Compensation - Summary of Stock Option Activity (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Shares, Beginning Balance	505,112
Granted, Shares	53,175
Exercised, Shares	(67,029)	(227,410)	(582,730)
Forfeited, Shares	(10,522)
Shares, Ending Balance	480,736	505,112
Vested or expected to vest, Shares	480,736
Exercisable, Shares	384,457
Weighted Average Exercise Price, Beginning Balance	$ 30.80
Granted, Weighted Average Exercise Price	$ 61.69
Exercised, Weighted Average Exercise Price	$ 26.17
Forfeited, Weighted Average Exercise Price	$ 54.41
Weighted Average Exercise Price, Ending Balance	$ 34.35	$ 30.80
Vested or expected to vest, Weighted Average Exercise Price	$ 34.35
Exercisable, Weighted Average Exercise Price	$ 27.37
Weighted Average Remaining Contractual Term, Ending Balance	4 years 5 months 5 days
Vested or expected to vest, Weighted Average Remaining Contractual Term	4 years 5 months 5 days
Exercisable, Weighted Average Remaining Contractual Term	3 years 4 months 13 days
Aggregate Intrinsic Value, Ending Balance	$ 2,757
Vested or expected to vest, Aggregate Intrinsic Value	2,757
Exercisable, Aggregate Intrinsic Value	$ 4,885