Statement of cash flow supplementary information (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 28, 2012	Dec. 30, 2011	Dec. 31, 2010
Supplemental cash flow disclosures of non-cash investing and financing activities [Abstract]
Capital expenditures included in accounts payable	$ 1,548	$ 1,245	$ 0
Debt issuance costs included in accounts payable	1,247	0	0
Common stock and warrant issued in connection with Oaktree recapitalization	29,603	0	0
Warrant issued in connection with senior credit facility amendment	2,013	0	0
Cash payments made during the year [Abstract]
Income taxes	10,039	8,147	9,544
Interest	$ 6,973	$ 6,145	$ 5,371