Restructuring Restructuring Plan (Details) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2018 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($) employee
Restructuring Reserve
Beginning balance	$ 185
Ending balance	185
2016 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Number of Positions Eliminated (in employee) | employee			7
Restructuring Reserve
Beginning balance	185	$ 273
Costs Incurred	0	0	$ 286
Cash Payments	0	(48)
Ending balance	$ 185	$ 225	$ 273