Summary of Stock Option Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Share-based Payment Arrangement [Abstract]
Shares, Options outstanding as of December 31, 2018	7,363,609
Shares, Granted	610,250
Shares, Exercised	(567,672)
Shares, Expired and forfeited	(141,952)
Shares, Options outstanding as of December 31, 2019	7,264,235	7,363,609
Shares, Options unvested at December 31, 2018	1,258,052
Shares, Exercisable at December 31, 2018	6,006,183
Weighted Average Exercise Price, Outstanding as of December 31, 2018	$ 63.06
Weighted Average Exercise Price, Granted	94.45
Weighted Average Exercise Price, Exercised	28.95
Weighted Average Exercise Price, Expired and forfeited	82.24
Weighted Average Exercise Price, Outstanding as of December 31, 2019	67.99	$ 63.06
Weighted Average Exercise Price, Options unvested at December 31, 2019	89.49
Weighted Average Exercise Price, Exercisable at December 31, 2019	$ 63.48
Weighted Average Remaining Years, Options outstanding	4 years 8 months 12 days	5 years 1 month 6 days
Weighted Average Remaining Years, Options unvested at December 31, 2019	8 years 6 months
Weighted Average Remaining Years, Exercisable at December 31, 2019	3 years 10 months 24 days
Aggregate Intrinsic Value, Options outstanding	$ 146,700	$ 183,091
Aggregate Intrinsic Value, Options unvested at December 31, 2019	447
Aggregate Intrinsic Value, Exercisable at December 31, 2019	$ 146,253
Closing price of common stock	$ 84.55