Revenue Disaggregation (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Total Revenue	$ 35,751	$ 35,775	$ 36,238	$ 35,606	$ 34,693	$ 34,756	$ 44,740	$ 42,284	$ 143,370	$ 156,473	$ 181,157
United States
Disaggregation of Revenue [Line Items]
Total Revenue									95,316	109,093	123,209
International
Disaggregation of Revenue [Line Items]
Total Revenue									48,054	47,380	57,948
Implant-based
Disaggregation of Revenue [Line Items]
Total Revenue									105,816	127,111	143,818
Implant-based | United States
Disaggregation of Revenue [Line Items]
Total Revenue									92,071	106,014	120,572
Implant-based | International
Disaggregation of Revenue [Line Items]
Total Revenue									13,745	21,097	23,246
Shipment-based
Disaggregation of Revenue [Line Items]
Total Revenue									37,554	29,362	37,339
Shipment-based | United States
Disaggregation of Revenue [Line Items]
Total Revenue									3,245	3,079	2,637
Shipment-based | International
Disaggregation of Revenue [Line Items]
Total Revenue									$ 34,309	$ 26,283	$ 34,702