Business and Organization (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Subsequent Event [Line Items]
Net loss	$ 16,240	$ 15,292
Accumulated deficit	(9,007)	(7,861)	$ (14,203)
Net cash used in operating activities	17,037	29,390
Cash and cash equivalents	17,417	17,515	29,268
Working capital	13,500
Accumulated deficit
Subsequent Event [Line Items]
Net loss	16,240	15,292
Accumulated deficit	$ 178,803	$ 162,563	$ 147,171