Summary of Stock Option Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Stock Option Shares
Grants outstanding at beginning of the period	8,391,171	8,806,204	5,436,951
Granted	1,429,652	2,152,439	4,805,722	[1]
Exercised	(1,055,715)	(2,119,306)	(792,845)
Expired and forfeited	(418,760)	(448,166)	(643,624)
Grants outstanding at end of the period	8,346,348	8,391,171	8,806,204
Grants exercisable at end of the period	2,368,621	2,304,791	3,288,712
Grants vested and expected to vest at end of the period	7,987,427	6,643,835	6,910,022
Weighted Average Exercise Price
Grants outstanding at beginning of the period	$ 46.09	$ 29.74	$ 22.70
Granted	132.97	90.15	35.09
Exercised	30.73	22.89	17.40
Expired and forfeited	84.15	46.11	25.44
Grants outstanding at end of the period	61.01	46.09	29.74
Grants exercisable at end of the period	45.33	27.69	24.76
Grants vested and expected to vest at end of the period	$ 58.65	$ 45.43	$ 28.49
Aggregate Intrinsic Value
Outstanding at end of year	$ 587,191
Exercisable at end of year	199,438
Vested and expected to vest	$ 578,938
Weighted Average Remaining Contractual Life (Years)
Outstanding at end of year	7 years 6 months
Exercisable at end of year	6 years
Vested and expected to vest	7 years 4 months 24 days

[1] Includes 3,300,000 options with service and market conditions granted to the Company’s CEO. These options have a five-year cliff vesting schedule. The fair value of $13.48 for these options was determined by a lattice model with Monte Carlo simulations.