Restructuring Costs (Details) - USD ($) $ in Thousands		3 Months Ended	6 Months Ended
	Apr. 17, 2018	Jun. 30, 2018	Jun. 30, 2018
Restructuring Cost and Reserve [Line Items]
Percentage of workforce reduced	40.00%
Charges incurred		$ 900
Amount paid		468
Remaining liability		432	$ 432
Net gain on sale or exchange of assets disposed			100
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		354
Remaining liability		432	$ 432
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