Business and Organization (Details) $ / shares in Units, $ in Thousands		3 Months Ended		9 Months Ended
	May 24, 2018 $ / shares	Sep. 30, 2018 USD ($) $ / shares	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) $ / shares	Sep. 30, 2017 USD ($)	Jul. 02, 2018 $ / shares	Dec. 31, 2017 USD ($) $ / shares	Dec. 31, 2016 USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Net loss		$ 2,859	$ 115	$ 8,654	$ 19,140
Cash used in operating activities				10,217	12,879
Cash and cash equivalents		16,111	$ 11,911	16,111	$ 11,911		$ 17,417	$ 17,515
Working capital		14,600		14,600
Accumulated deficit		$ 187,457		$ 187,457			$ 178,803
Stock split, conversion ratio	0.2
Common stock, par value (in dollars per share) | $ / shares	$ 0.001	$ 0.001		$ 0.001		$ 0.001	$ 0.001
Stockholders equity		$ 10,184		$ 10,184			$ 9,007