Stock-Based Compensation - Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Stock-Based Compensation Expense
Stock-based compensation expense	$ 264,318	$ 93,273	$ 49,619
Cost of revenue
Stock-Based Compensation Expense
Stock-based compensation expense	7,123	1,126	650
Research and development
Stock-Based Compensation Expense
Stock-based compensation expense	126,012	42,277	22,808
Sales and marketing
Stock-Based Compensation Expense
Stock-based compensation expense	60,886	23,616	9,822
General and administrative
Stock-Based Compensation Expense
Stock-based compensation expense	70,297	$ 26,254	$ 16,339
SendGrid
Stock-Based Compensation Expense
Stock-based compensation expense	$ 81,800