INCOME TAXES - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Jan. 02, 2016
Federal:
Current	$ 613	$ (71)
Deferred	1,284	737
State:
Current	2	2
Deferred	249	113
Total	$ 2,148	$ 781
Difference between tax rate on income for financial statement purposes and federal statutory tax rate
Statutory tax rate (as a percent)	34.00%	34.00%
Percentage depletion (as a percent)	(1.80%)	(4.00%)
Non-deductible expenses (as a percent)	1.00%	2.00%
Valuation allowance for tax assets (as a percent)	1.00%	(4.90%)
State income taxes, net of federal benefit (as a percent)	4.20%	5.70%
Expiring charitable contributions (as a percent)		2.60%
Domestic production deduction (as a percent)	(0.80%)
Other (as a percent)	(0.80%)	0.20%
Total (as a percent)	36.80%	35.60%
Current statutory federal and states tax rates (as a percent)	37.96%
Deferred tax assets
Reserves for self-insured losses	$ 579	$ 605
Accrued reclamation	1,945	2,154
Unfunded supplemental profit sharing plan liability	351	379
Asset valuation reserves	267	317
Future state tax credits	789	789
Net state operating loss carryforwards	167	252
Federal AMT carryforward	620	481
Federal NOL carryforward		16
Other	873	746
Deferred tax asset before deferred tax liabilities and valuation allowance	5,591	5,739
Net deferred tax asset before valuation allowance	1,746	3,222
Valuation allowance	(73)	(180)
(Increase) decrease during the period	(57)	107
Valuation allowance	(130)	(73)
Net deferred tax asset	1,616	3,149
Deferred tax liabilities
Depreciation	1,013	841
Deferred development	1,057	563
Prepaid royalties	1,187	478
Other	588	635
Total deferred tax liabilities	$ 3,845	$ 2,517