Restructuring Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Restructuring Cost and Reserve [Line Items]
Costs incurred and charged to expense	$ 6,418	$ 49,090	$ (7,263)
Restructuring Reserve, Current	32,500	26,200
Restructuring Reserve, Noncurrent	$ 7,600	$ 21,800