SCHEDULE II-VALUATION AND QUALIFYING ACCOUNTS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 26, 2020	Dec. 28, 2019	Dec. 29, 2018
SEC Schedule, 12-09, Allowance, Credit Loss [Member]
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of year	$ 770	$ 836	$ 980
Charged to costs and expenses	1,208	(81)	(286)
Other additions	0	263	220
Deductions	440	248	78
Balance at end of year	1,538	770	836
Environmental Reserves [Member]
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of year	20,866	23,619	28,004
Charged to costs and expenses	4,242	1,659	1,981
Other additions	0	0	0
Deductions	1,107	4,412	6,366
Balance at end of year	24,001	20,866	23,619
SEC Schedule, 12-09, Valuation Allowance, Deferred Tax Asset [Member]
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of year	23,130	25,311	30,316
Charged to costs and expenses	2,317	2,919	1,209
Other additions	1,898	290	150
Deductions	146	5,390	6,364
Balance at end of year	$ 27,199	$ 23,130	$ 25,311