NATURE OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Other Assets (Details)		12 Months Ended
	Nov. 16, 2018 USD ($)	Dec. 29, 2018 USD ($) item	Dec. 30, 2017 USD ($)	Dec. 31, 2016 USD ($)
Amortizable intangible assets
Goodwill impairment charges recognized		$ 0	$ 0
Other long-term assets		$ 547,000	$ 3,769,000
Number of aggregate property leases which require royalty payments to which the entity is a party | item		3
Claim to recover royalty overpayments	$ 1,470,000
Wrote off the remaining royalty overpayment		$ 627,000
Charges Related to Cessation of Mining		$ 6,840,000
Aggregate property near Colorado Springs [Member]
Amortizable intangible assets
Other long-term assets				$ 2,500,000