Quarterly report pursuant to Section 13 or 15(d)

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

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Accumulated Other Comprehensive Loss and Other Comprehensive Income - Components of Accumulated Other Comprehensive Loss (Details) - USD ($)
$ in Thousands
3 Months Ended
Mar. 31, 2018
Apr. 01, 2017
Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]      
Total Shareholders’ Equity $ 338,028   $ 329,927
Adoption of ASU 2018-02 1,400    
Foreign Currency Translation Adjustments      
Accumulated Other Comprehensive Income (Loss) [Line Items]      
Total Shareholders’ Equity (4,232)   (4,465)
Retirement Liability Adjustment      
Accumulated Other Comprehensive Income (Loss) [Line Items]      
Total Shareholders’ Equity (10,045)   (8,887)
Retirement Liability Adjustment – Before Tax (12,715)   (12,988)
Tax Benefit of Retirement Liability Adjustment 4,043   4,101
Adoption of ASU 2018-02 (1,373) $ 0  
Accumulated Other Comprehensive Loss      
Accumulated Other Comprehensive Income (Loss) [Line Items]      
Total Shareholders’ Equity (14,277)   $ (13,352)
Adoption of ASU 2018-02 $ (1,373)