Equity Incentive Plans - Schedule of Non-cash Share-Based Compensation Expenses Related to Company's Equity-Based Awards (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total share-based compensation expense	$ 10,479	$ 8,629	$ 29,205	$ 20,760	$ 27,116
Cost of Revenues
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total share-based compensation expense	464	79	891	353	467
Research, Development and Clinical Trials
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total share-based compensation expense	1,223	972	3,415	2,645	3,587
Sales and Marketing
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total share-based compensation expense	1,979	1,874	5,309	4,264	3,784
General and Administrative
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total share-based compensation expense	$ 6,813	$ 5,704	$ 19,590	$ 13,498	$ 19,278