Summary of Stock Option Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Stock Option Shares
Grants outstanding at beginning of the period	8,346,348	8,391,171	8,806,204
Granted	1,402,409	1,429,652	2,152,439
Exercised	(1,445,054)	(1,055,715)	(2,119,306)
Cancelled and forfeited	(458,756)	(418,760)	(448,166)
Grants outstanding at end of the period	7,844,947	8,346,348	8,391,171
Grants exercisable at end of the period	2,020,322	2,368,621	2,304,791
Grants vested and expected to vest at end of the period	7,500,726	7,987,427	6,643,835
Weighted Average Exercise Price
Grants outstanding at beginning of the period	$ 61.01	$ 46.09	$ 29.74
Granted	122.25	132.97	90.15
Exercised	53.21	30.73	22.89
Cancelled and forfeited	108.60	84.15	46.11
Grants outstanding at end of the period	70.61	61.01	46.09
Grants exercisable at end of the period	70.16	45.33	27.69
Grants vested and expected to vest at end of the period	$ 68.24	$ 58.65	$ 45.43
Aggregate Intrinsic Value
Outstanding at end of year	$ 783,558
Exercisable at end of year	202,709
Vested and expected to vest	$ 766,936
Weighted Average Remaining Contractual Life (Years)
Outstanding at end of year	7 years
Exercisable at end of year	6 years 2 months 12 days
Vested and expected to vest	6 years 10 months 24 days