Intangible assets, net (Details) (USD $)	12 Months Ended
	Dec. 28, 2012	Dec. 30, 2011	Dec. 31, 2010
Finite Lived Intangible Assets [Line Items]
Intangible assets subject to amortization (definite lives)	$ 5,300,000	$ 5,300,000
Accumulated amortization	(4,833,000)	(4,365,000)
Net intangible assets subject to amortization	467,000	935,000
Indefinite-lived Intangible Assets [Line Items]
Intangible assets, net	3,067,000	3,535,000
Weighted average life of finite intangible assets	1 year
Amortization expense for period	500,000	1,300,000	2,300,000
Tradename [Member]
Indefinite-lived Intangible Assets [Line Items]
Intangible assets not subject to amortization (indefinite lives)	2,600,000	2,600,000
Customer relationships [Member]
Finite Lived Intangible Assets [Line Items]
Intangible assets subject to amortization (definite lives)	3,300,000	3,300,000
Accumulated amortization	(2,833,000)	(2,365,000)
Technology [Member]
Finite Lived Intangible Assets [Line Items]
Intangible assets subject to amortization (definite lives)	2,000,000	2,000,000
Accumulated amortization	$ (2,000,000)	$ (2,000,000)