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EMPLOYEE BENEFIT PLANS - Defined Contribution Plan (Details) - USD ($)
12 Months Ended
Dec. 26, 2018
Dec. 27, 2017
Dec. 28, 2016
Defined Benefit Plan Disclosure [Line Items]      
Employer contributions $ 509,000 $ 389,000 $ 257,000
Defined Contribution Plan, Initial Contribution      
Defined Benefit Plan Disclosure [Line Items]      
Employer matching contribution percentage 100.00%    
Employer matching contribution as a percent of employees' gross pay 3.00%    
Defined Contribution Plan, Additional Contribution      
Defined Benefit Plan Disclosure [Line Items]      
Employer matching contribution percentage 50.00%    
Employer matching contribution as a percent of employees' gross pay 3.00%    
Defined Contribution Plan, Additional Contribution | Maximum      
Defined Benefit Plan Disclosure [Line Items]      
Employer matching contribution as a percent of employees' gross pay 5.00%