Quarterly report pursuant to Section 13 or 15(d)

Basis of Presentation (Details)

v3.10.0.1
Basis of Presentation (Details)
$ in Thousands
3 Months Ended 9 Months Ended
Oct. 12, 2018
Sep. 29, 2018
USD ($)
Mar. 31, 2018
USD ($)
Sep. 30, 2017
USD ($)
Sep. 29, 2018
USD ($)
Sep. 30, 2017
USD ($)
Jan. 01, 2018
USD ($)
Dec. 31, 2017
USD ($)
Business Acquisition [Line Items]                
Research and development, design and related engineering   $ 31,200   $ 23,700 $ 89,000 $ 69,500    
Adoption of ASU 2018-02     $ 1,400          
Convertible Class B Stock | Subsequent Event                
Business Acquisition [Line Items]                
Stock split ratio, common stock 0.15              
ACCUMULATED OTHER COMPREHENSIVE LOSS                
Business Acquisition [Line Items]                
Adoption of ASU 2018-02         (1,373)      
RETAINED EARNINGS                
Business Acquisition [Line Items]                
Adoption of ASU 2018-02         1,373      
Accounting Standards Update 2014-09 | RETAINED EARNINGS                
Business Acquisition [Line Items]                
Adoption of ASU 2014-09             $ 3,300 $ 3,268
Selling, General and Administrative Expenses | Accounting Standards Update 2017-07                
Business Acquisition [Line Items]                
Other net periodic benefit costs   500   400 1,500 1,300    
Other Expense | Accounting Standards Update 2017-07                
Business Acquisition [Line Items]                
Other net periodic benefit costs   $ (500)   $ (400) $ (1,000) $ (900)