Special charges (Details) (USD $)	3 Months Ended	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2012
Special Charges [Line Items]
Patent settlements with non-practicing entities		$ 1,700,000
Associated liabilities incurred related to plan [Roll Forward]
Beginning Balance		0
Charged to expense		2,191,000
Paid or otherwise settled		(254,000)
Ending Balance	1,937,000	1,937,000
Severance and Personnel Costs [Member]
Associated liabilities incurred related to plan [Roll Forward]
Beginning Balance		0
Charged to expense		281,000
Paid or otherwise settled		(116,000)
Ending Balance	165,000	165,000
Other Exit Costs [Member]
Associated liabilities incurred related to plan [Roll Forward]
Beginning Balance		0
Charged to expense		1,910,000
Paid or otherwise settled		(138,000)
Ending Balance	1,772,000	1,772,000
Technology Products [Member]
Special Charges [Line Items]
Special charges	200,000	2,100,000
Patent settlements with non-practicing entities	1,700,000	1,700,000
Severance costs	100,000	100,000
Industrial Products [Member]
Special Charges [Line Items]
Special charges	$ 0	$ 2,200,000