Stock-Based Compensation - Summary of Total Stock-based Compensation Expense by Function (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share based compensation expense	$ 11,374	$ 141	$ 24,747	$ 482
Sales and Distribution Expenses
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share based compensation expense	2,421	5	5,218	11
Research and Development Expense
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share based compensation expense	1,920	8	3,952	21
General and Administrative Expense
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share based compensation expense	$ 7,033	$ 128	$ 15,577	$ 450