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]
Year ended:
Balance at beginning of year		$ 262	$ 174	$ 133
Charged to costs and expenses		90	240	162
Charged to other accounts		0	0	0
Deductions	[1]	208	152	121
Balance at end of year		144	262	174
Provision for claims, allowances and warranties [Member]
Year ended:
Balance at beginning of year		4,541	5,717	6,360
Charged to costs and expenses		7,938	10,538	11,995
Charged to other accounts		0	0	0
Deductions		7,999	11,714	12,638	[2]
Balance at end of year		$ 4,480	$ 4,541	$ 5,717

[1] Uncollectible accounts written off, net of recoveries.

[2] Net reserve reductions for claims, allowances and warranties settled.