Income Taxes (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating Loss Carryforwards [Line Items]
Obligation for transition tax liability, net of tax credits	$ 17,100	$ 17,100
Net increase (decrease) in deferred tax asset valuation allowance		28,600	$ 34,300
Deferred tax expense to reflect the reduced tax rate and related effects	600
Tax Cuts and Jobs Act, Incomplete Accounting, Change in Tax Rate, Valuation Allowance, Provisional Income Tax Expense	100
Net tax expense not offset by change in valuation allowance	700
Valuation allowance of deferred tax assets	119,494	119,494	90,900
Net expense related to increase in unrecognized tax benefits		1,500
Income tax penalties and interest		200	200	$ 200
Interest from settlements, lapse of statutes, and change in certainty released		200
Cumulative accrued balance of penalties and interest	700	700	600	500
Unrecognized tax benefits that would impact effective tax rate	6,200	6,200	4,800	$ 5,000
Deferred tax assets related to U.S. federal tax carryforwards	48,600	48,600	57,300
Deferred tax assets related to U.S. state tax carryforwards	12,500	12,500	9,400
Deferred tax assets related to foreign tax carryforwards	49,500	49,500	39,300
European, South American and Asian jurisdictions [Member]
Operating Loss Carryforwards [Line Items]
Aggregate tax loss carryforward	$ 18,800	18,800
Valuation Allowance Related To Income Tax Expense [Member]
Operating Loss Carryforwards [Line Items]
Net increase (decrease) in deferred tax asset valuation allowance		24,400	16,000
Valuation Allowance, Impact of Unrecorded Tax Attributes Related to Changes in Cumulative Translation Adjustments [Member]
Operating Loss Carryforwards [Line Items]
Net increase (decrease) in deferred tax asset valuation allowance		$ 4,200	$ 18,300