Accrued Expenses Components of Accrued Expenses (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Payables and Accruals [Abstract]
Salaries and wages	$ 33,134	$ 33,390
Warranty cost	22,159	22,468
Taxes other than income taxes, primarily Value Added Taxes	18,458	22,627
Professional	5,029	5,203
Deferred revenue	4,591	2,770
Freight	4,225	4,002
Rebates	3,650	5,831
Interest	3,406	3,919
Product liability, current portion	2,857	2,905
Derivative liabilities (foreign currency forward exchange contracts)	2,652	2,120
Severance	1,799	3,704
Rent	772	808
Insurance	698	645
Supplemental Executive Retirement Program liability	391	391
Other items, principally trade accruals	7,829	7,914
Accrued expenses	$ 111,650	$ 118,697