Share Based Awards - Compensation expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Allocation of employee service stock-based compensation expense
Stock-based compensation expense	$ 7,573	$ 10,290
Cost of revenue
Allocation of employee service stock-based compensation expense
Stock-based compensation expense	898	1,541
Research and development
Allocation of employee service stock-based compensation expense
Stock-based compensation expense	3,059	4,111
Sales and marketing
Allocation of employee service stock-based compensation expense
Stock-based compensation expense	2,073	2,274
General and administrative
Allocation of employee service stock-based compensation expense
Stock-based compensation expense	$ 1,543	$ 2,364