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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Stock Plans (Details) - Stock Option Plans - USD ($)
$ in Thousands
3 Months Ended
Mar. 31, 2018
Apr. 01, 2017
Defined Benefit Plan Disclosure [Line Items]    
Shares of common stock available for issuance (in shares) 550,606  
Compensation expense $ 1,090 $ 1,289
Income tax benefits $ 273 $ 496
Minimum    
Defined Benefit Plan Disclosure [Line Items]    
Vesting period of options 3 years  
Expiration period of grant 6 years  
Maximum    
Defined Benefit Plan Disclosure [Line Items]    
Vesting period of options 7 years  
Expiration period of grant 10 years