Financial instruments and fair value measurements (Details Textual)	6 Months Ended						6 Months Ended
	Jun. 30, 2012 USD ($)	Dec. 31, 2011 USD ($)	Dec. 31, 2011 EUR (€)	Mar. 31, 2011	Jun. 30, 2012 Minimum [Member] USD ($)	Jun. 30, 2012 Maximum [Member] USD ($)	Jun. 30, 2012 Chemicals [Member] USD ($)	Jun. 30, 2012 Component Products [Member] USD ($)	Jun. 30, 2012 Canadian Dollars [Member]	Jun. 30, 2012 Canadian Dollars [Member] Chemicals [Member] USD ($)	Jun. 30, 2012 Canadian Dollars [Member] Component Products [Member]	Jun. 30, 2012 Norwegian Kroner [Member] Chemicals [Member] USD ($)
Segment Reporting Information [Line Items]
Notional amount currency forward contract								$ 8,800,000		$ 24,000,000		$ 30,000,000
Exchange floor rate										1.0	1.03	5.99
Exchange cap rate										1.03		6.05
Exchange rate									1.02
Maturity rate of derivative										4,000,000		5,000,000
Estimated fair value of these currency forward contracts							100,000
Estimated fair value of currency forward contracts, assets								100,000
Estimated fair value of these currency forward contracts, part of accounts and other receivables							200,000
Estimated fair value of these currency forward contracts, part of accounts payable and accrued liabilities		800,000					300,000
Currency transaction gain							100,000
Interest rate of note		6.50%	6.50%	6.50%
Potential additional cash consideration related to ergonomics healthcare product line acquired by Component Products Segment						1,500,000
Financial instruments and fair value measurements (Textual) [Abstract]
Estimated market price of the notes			1,004
Principal amount of notes outstanding			1,000
Redemption price of investment	$ 250,000,000
Discount rate related to fair value	4.00%