Related Party Transactions - Additional Information (Details) - USD ($) $ in Thousands			1 Months Ended			9 Months Ended
	Jul. 01, 2016	Aug. 13, 2014	Sep. 30, 2014	Apr. 30, 2014	Mar. 31, 2014	Sep. 30, 2018	Dec. 31, 2017
Related Party Transaction [Line Items]
Settlement amount to be contributed						$ 5,000	$ 5,000
Orthotec LLC, litigation settlement
Related Party Transaction [Line Items]
Payments of settlement				$ 15,750	$ 1,750	35,100
Judgment assessed by court for (against) company		$ (49,000)
Orthotec LLC, litigation settlement | HealthpointCapital, LLC
Related Party Transaction [Line Items]
Payments of settlement	$ 1,000					1,100
Judgment assessed by court for (against) company			$ (5,000)
Settlement amount to be contributed						$ 5,000