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Stockholders' Equity - Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation	$ 32,922	$ 24,297	$ 60,478	$ 48,588
Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized stock-based compensation expense	35,043		$ 35,043
Weighted-average amortization period			2 years 10 months 24 days
RSU
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized stock-based compensation expense	360,713		$ 360,713
Weighted-average amortization period			3 years 8 months 12 days
ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized stock-based compensation expense	5,793		$ 5,793
Weighted-average amortization period			10 months 24 days
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized stock-based compensation expense	3,206		$ 3,206
Weighted-average amortization period			2 years 2 months 12 days
Cost of revenue
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation	1,585	1,028	$ 2,912	2,126
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation	19,378	12,568	35,306	25,699
Sales and marketing
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation	8,277	7,097	14,673	13,631
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation	$ 3,682	$ 3,604	$ 7,587	$ 7,132