Assets held for sale and discontinued operations (Details) (USD $) In Thousands, unless otherwise specified	1 Months Ended	3 Months Ended	12 Months Ended
	Jan. 31, 2009	Dec. 31, 2011	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Assets held for sale and discontinued operations [Abstract]
Gross cash proceeds from sale of business	$ 250
Revenue				0	816
Loss from operations				0	(155)
(Loss) gain on disposal				(1,244)	155
Income tax benefit				473	0
Net loss from discontinued operations			0	(771)	0
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Asset impairment charges		1,196	1,196	0	24,900
Greensboro facility [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net cash proceeds from sale of facility			699
Pre-tax gain from sale of facility			110
Thorofare facility [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Asset impairment charges			$ 1,196