Property and Equipment, net (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property and equipment, Gross	$ 1,336	$ 1,336		$ 1,336
Less: Accumulated depreciation	(891)	(891)		(811)
Property and equipment, net	445	445		525
Depreciation	100	80	$ 91
Computer equipment
Property, Plant and Equipment [Line Items]
Property and equipment, Gross	329	329		329
Office and other equipment
Property, Plant and Equipment [Line Items]
Property and equipment, Gross	301	301		301
Laboratory equipment
Property, Plant and Equipment [Line Items]
Property and equipment, Gross	643	643		643
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, Gross	$ 63	$ 63		$ 63