Revenue Disaggregation (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Disaggregation of Revenue [Line Items]
Revenue	$ 24,841	$ 36,238	$ 53,351	$ 71,844
United States
Disaggregation of Revenue [Line Items]
Revenue	14,230	24,013	32,859	46,798
International
Disaggregation of Revenue [Line Items]
Revenue	10,611	12,225	20,492	25,046
Implant-based
Disaggregation of Revenue [Line Items]
Revenue	15,795	26,744	37,110	53,013
Implant-based | United States
Disaggregation of Revenue [Line Items]
Revenue	13,755	23,507	32,078	45,969
Implant-based | International
Disaggregation of Revenue [Line Items]
Revenue	2,040	3,237	5,032	7,044
Shipment-based
Disaggregation of Revenue [Line Items]
Revenue	9,046	9,494	16,241	18,831
Shipment-based | United States
Disaggregation of Revenue [Line Items]
Revenue	475	506	781	829
Shipment-based | International
Disaggregation of Revenue [Line Items]
Revenue	$ 8,571	$ 8,988	$ 15,460	$ 18,002