Restructuring (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended			36 Months Ended
	Dec. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2017
Restructuring Cost and Reserve [Line Items]
Restructuring charges accrued		$ 5,000			$ 14,800
Non-cash restructuring charges relating to impairment of long-lived assets		4,500
Fair value adjustment on available-for-sale assets				$ 3,212
Restructuring reserve, current		2,714	4,668		2,714
Restructuring reserve, noncurrent		600	908		$ 600
Payments for restructuring		1,600
Former Employee [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges accrued			1,600
Reduced Employee Expenses [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges accrued		800	2,600	11,400
Fair value adjustment on available-for-sale assets				3,300
Early Retirement Program [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges accrued	$ 8,100
Machine Clothing [Member]
Restructuring Cost and Reserve [Line Items]
Write-off of equipment			$ 2,200
Payments for restructuring		$ 1,100
Machine Clothing and Corporate [Member] | Early Retirement Program [Member]
Restructuring Cost and Reserve [Line Items]
Effect of cost savings				$ 4,300