Restructuring (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2017 USD ($)
Research and development and selling, general and administrative expenses
Restructuring Cost and Reserve [Line Items]
Work-force reduction charges	$ 2,500
2016 Workforce Reduction
Restructuring Reserve [Roll Forward]
Restructuring Reserve, Beginning Balance	22
Expenses, net	0
Cash payments	(22)
Restructuring Reserve, Ending Balance	$ 0