Restructuring - Schedule of Restructuring (Details) - Termination Benefits - Accrued liabilities - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance	$ 31	$ 1,105
Expense	14	1,516
Payments	(45)	(2,590)
Restructuring reserve, ending balance	$ 0	$ 31