Stockholders' Equity - Stock-Based Compensation Expense Recognized in Company's Condensed Consolidated Statement of Operations (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Cash paid to accelerate vesting	$ 75,844	$ 61,519	$ 156,410	$ 110,542
Cost of revenues
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Cash paid to accelerate vesting	7,655	6,500	16,998	11,512
Sales and marketing
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Cash paid to accelerate vesting	18,215	15,157	36,760	28,458
General and administrative
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Cash paid to accelerate vesting	$ 49,974	$ 39,862	$ 102,652	$ 70,572