Quarterly report pursuant to Section 13 or 15(d)

Accumulated Other Comprehensive Loss and Other Comprehensive Income - Components of Other Comprehensive Income (Details)

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Accumulated Other Comprehensive Loss and Other Comprehensive Income - Components of Other Comprehensive Income (Details) - USD ($)
$ in Thousands
3 Months Ended 6 Months Ended
Jun. 30, 2018
Jul. 01, 2017
Jun. 30, 2018
Jul. 01, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]        
Other Comprehensive Income $ (1,590) $ 2,227 $ (1,142) $ 2,753
Foreign Currency Translation Adjustments        
Accumulated Other Comprehensive Income (Loss) [Line Items]        
Other Comprehensive Income (1,805) 2,096 (1,572) 2,491
Amortization of Prior Service Cost        
Reclassifications to General and Administrative Expense:        
Reclassifications to General and Administrative Expense 101 102 202 202
Amortization of Net Actuarial Losses        
Reclassifications to General and Administrative Expense:        
Reclassifications to General and Administrative Expense 172 99 343 201
Retirement Liability Adjustment        
Accumulated Other Comprehensive Income (Loss) [Line Items]        
Other Comprehensive Income 215 131 430 262
Reclassifications to General and Administrative Expense:        
Tax Benefit $ (58) $ (70) $ (115) $ (141)