EMPLOYEE DEFINED CONTRIBUTION PLANS - (Details) - USD ($)		12 Months Ended
	Jan. 01, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Maximum amount of employer match per employee		$ 2,000
Meximum semi-annual amount of employer match per employee		1,000
Defined contribution expense		$ 1,400,000	$ 600,000
Subsequent Event
Defined Benefit Plan Disclosure [Line Items]
Employer matching percent of employees' contribution	50.00%
Employer matching contribution percentage of employees' gross pay	4.00%
Maximum employer match percentage per employee	2.00%