Share Option Plan and ESPP - Schedule of Non-cash Share-Based Compensation Expenses Related to Company's Equity-Based Awards (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation expense	$ 16,557	$ 9,649	$ 52,416
Cost of revenues
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation expense	590	426	2,231
Research, development and clinical trials
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation expense	3,394	1,188	7,570
Sales and marketing
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation expense	3,616	1,962	11,897
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total share-based compensation expense	$ 8,957	$ 6,073	$ 30,718