Intangible assets (Details) (USD $)	6 Months Ended
	Jul. 01, 2011	Jun. 25, 2010	Dec. 31, 2010
Finite-Lived Intangible Assets [Line Items]
Intangible assets subject to amortization (definite lives)	$ 6,260,000		$ 6,260,000
Accumulated amortization	(3,929,000)		(3,203,000)
Net intangible assets subject to amortization	2,331,000		3,057,000
Intangible assets, net [Abstract]
Intangible assets, net	4,931,000		5,657,000
Finite-lived intangible assets [Abstract]
Amortization expense for period	700,000	1,400,000
Weighted average life of finite intangible assets (in years)	1.9
2012	539,000
2013	539,000
2014	68,000
2015	68,000
2016	68,000
Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible assets subject to amortization (definite lives)	3,300,000		3,300,000
Accumulated amortization	(2,132,000)		(1,897,000)
Technology [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible assets subject to amortization (definite lives)	2,000,000		2,000,000
Accumulated amortization	(1,651,000)		(1,178,000)
Other [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible assets subject to amortization (definite lives)	960,000		960,000
Accumulated amortization	(146,000)		(128,000)
Tradename [Member]
Indefinite-lived Intangible Assets by Major Class [Line Items]
Intangible assets not subject to amortization (indefinite lives)	$ 2,600,000		$ 2,600,000