Supplementary information (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 30, 2011	Dec. 31, 2010	Dec. 25, 2009
Other Costs Charged to Expense [Abstract]
Depreciation	$ 8,597	$ 15,073	$ 14,891
Amortization of intangible assets	1,295	2,337	3,563
Advertising	164	159	136
Repairs and maintenance	7,664	11,263	8,879
Bad debt expense	28	128	330
Cash payments made [Abstract]
Income taxes	8,147	9,544	7,256
Interest	6,145	5,371	1,989
Supplemental schedule of non-cash financing and investing activities:
Change in accrued capital expenditures	$ 1,245	$ 0	$ 0