Restructuring - Restructuring Activities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Restructuring Reserve [Roll Forward]
Accrued restructuring balance as of December 31, 2016	$ 3,406
Restructuring	4,030	$ 5,400	$ 0
Payments	(6,551)
Accrued restructuring balance as of December 31, 2017	403	$ 3,406
Severance
Restructuring Reserve [Roll Forward]
Restructuring	3,048
Other
Restructuring Reserve [Roll Forward]
Restructuring	$ 500