Entity Wide Disclosures - Summary of Revenue by Major Source (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation Of Revenue [Line Items]
Total revenue	$ 216,238	$ 179,253	$ 631,083	$ 512,474
Oncology
Disaggregation Of Revenue [Line Items]
Total revenue	65,529	48,947	186,152	135,824
Other
Disaggregation Of Revenue [Line Items]
Total revenue	53,484	42,200	158,676	114,852
Metabolic
Disaggregation Of Revenue [Line Items]
Total revenue	34,919	30,037	102,287	90,748
AVAI
Disaggregation Of Revenue [Line Items]
Total revenue	24,243	21,947	66,831	59,497
Cardiology
Disaggregation Of Revenue [Line Items]
Total revenue	21,733	22,227	68,792	71,262
Central Nervous System
Disaggregation Of Revenue [Line Items]
Total revenue	$ 16,330	$ 13,895	$ 48,345	$ 40,291