Restructuring Charges (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Restructuring and Related Activities [Abstract]
Restructuring, expected cost	$ 12,600
Restructuring Reserve [Roll Forward]
Accrual, beginning balance	2,754
Restructuring costs	1,477	$ 11,093	$ 0
Utilization	(3,223)
Accrual, ending balance	$ 1,008	$ 2,754