Significant Accounting Policies (Details) - USD ($) $ in Thousands		6 Months Ended
	Jan. 01, 2019	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Group purchasing organization administrative fees (percent)		3.00%
Patent application costs		$ (253)	$ (40)
Right of use asset		3,852		$ 0
Operating lease liability		$ 4,611
Accounting Standards Update 2016-02
Finite-Lived Intangible Assets [Line Items]
Right of use asset	$ 4,300
Rent credit	900
Operating lease liability	5,200
Effect on opening retained earnings	$ 0