Segment Information (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) item	Sep. 30, 2014 USD ($)
Segment Information
Number of reportable segments | item			3
Segment Information
Net Sales	$ 132,976	$ 137,699	$ 404,131	$ 414,463
Income from operations	16,968	18,868	54,053	55,794
Restructuring income		27		252
Interest income	6	15	51	56
Interest expense	(254)	(32)	(500)	(196)
Other income (expense) - net	890	(401)	(261)	(1,329)
Income before income tax provision	17,610	18,450	53,343	54,325
Depreciation and amortization	8,624	7,570	25,788	22,124
Activated Carbon and Service
Segment Information
Net Sales	121,330	124,372	367,644	372,043
Depreciation and amortization	7,954	6,742	23,461	19,484
Equipment
Segment Information
Net Sales	9,659	10,803	30,003	33,107
Depreciation and amortization	514	698	1,864	2,188
Consumer
Segment Information
Net Sales	1,987	2,524	6,484	9,313
Depreciation and amortization	156	130	463	452
Business operating segments
Segment Information
Income from operations	16,968	18,841	54,053	55,542
Business operating segments | Activated Carbon and Service
Segment Information
Income from operations	18,054	20,010	55,696	58,537
Business operating segments | Equipment
Segment Information
Income from operations	(1,278)	(1,481)	(2,680)	(4,587)
Business operating segments | Consumer
Segment Information
Income from operations	$ 192	$ 312	$ 1,037	$ 1,592