Patents and other intangible assets (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Intangible assets
Cost	$ 97,354,000	$ 94,459,000
Patents and other intangible assets, net	37,515,000	41,457,000
Future Amortization expense
2012	5,100,000
2013	4,500,000
2014	1,500,000
2015	1,400,000
2016	900,000
2017 and thereafter	1,100,000
Patents and developed technologies
Intangible assets
Cost	29,065,000	26,226,000
Accumulated amortization	(22,073,000)	(18,267,000)
Trademarks - definite lived (subject to amortization)
Intangible assets
Cost	646,000	543,000
Accumulated amortization	(416,000)	(337,000)
Trademarks - indefinite lived (not subject to amortization)
Intangible assets
Cost	23,057,000	23,104,000
Distribution networks
Intangible assets
Cost	44,586,000	44,586,000
Accumulated amortization	$ (37,350,000)	$ (34,398,000)