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INVESTMENTS IN SECURITIES (Details) - USD ($)
$ in Thousands
3 Months Ended 6 Months Ended
Jul. 01, 2018
Jun. 25, 2017
Jul. 01, 2018
Jun. 25, 2017
Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]          
Gross realized gains $ 1,800 $ 1,000 $ 2,900 $ 1,100  
Fixed income securities          
Debt Securities, Available-for-sale [Line Items]          
Amortized Cost 524,806   524,806   $ 330,456
Fair Value 524,806   524,806   330,456
Other          
Debt Securities, Available-for-sale [Line Items]          
Amortized Cost 1,323   1,323   942
Fair Value $ 1,323   $ 1,323   $ 942