Business and Organization (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Net loss	$ 2,901	$ 5,007
Cash used in operating activities	4,761	4,754
Cash and cash equivalents	12,201	$ 20,560	$ 17,417	$ 17,515
Working capital	10,800
Accumulated deficit	181,704		178,803
Stockholders equity	$ 6,259		$ 9,007