INCOME TAXES - Schedule of Deferred Tax Assets (Details) - USD ($) $ in Thousands	Dec. 30, 2018	Dec. 31, 2017
Deferred tax assets:
Net operating losses	$ 37,527	$ 37,631
Capital losses		1,726
Accruals and reserves	1,370	1,487
Credits carryforward	5,836	5,743
Depreciation and amortization	9,887	9,056
Stock-based compensation	347	343
Deferred tax assets, gross	54,967	55,986
Valuation allowances	(54,913)	(55,931)
Deferred tax asset	54	55
Deferred tax liability	$ 0	$ 0