Restructuring Costs (Details) - USD ($) $ in Thousands		3 Months Ended	9 Months Ended
	Apr. 17, 2018	Sep. 30, 2018	Sep. 30, 2018
Restructuring Cost and Reserve [Line Items]
Percentage of workforce reduced	40.00%
Charges incurred		$ 0	$ 900
Amount paid			696
Remaining liability		204	204
Net gain on sale or exchange of assets disposed			300
General and administrative
Restructuring Cost and Reserve [Line Items]
Charges incurred		400
Research and development
Restructuring Cost and Reserve [Line Items]
Charges incurred		500
Employee severance, benefits and related costs
Restructuring Cost and Reserve [Line Items]
Charges incurred			786
Amount paid			582
Remaining liability		$ 204	204
Consolidation of facilities
Restructuring Cost and Reserve [Line Items]
Charges incurred			98
Amount paid			98
Contract terminations
Restructuring Cost and Reserve [Line Items]
Charges incurred			16
Amount paid			$ 16