Restructuring, Acquisition and Integration (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2018	Dec. 31, 2017	Dec. 31, 2016
Restructuring Reserve [Roll Forward]
Balance at December 31, 2017		$ 7,681
Restructuring charges		36,103
Cash payments / adjustments		(33,534)
Balance at September 30, 2018	$ 10,250	10,250	$ 7,681
Employee severance & termination benefits
Restructuring Reserve [Roll Forward]
Balance at December 31, 2017		4,379
Restructuring charges	4,300	35,979	13,300	$ 96,300
Cash payments / adjustments		(32,624)
Balance at September 30, 2018	7,734	7,734	4,379
Contractual obligations and other
Restructuring Reserve [Roll Forward]
Balance at December 31, 2017		3,302
Restructuring charges		124
Cash payments / adjustments		(910)
Balance at September 30, 2018	$ 2,516	$ 2,516	$ 3,302