Segment Information - Results of Operations (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($) segment	Sep. 30, 2015 USD ($)
Segment Information
Number of reportable segments | segment			3
Net Sales	$ 123,970	$ 132,976	$ 376,766	$ 404,131
Income (loss) from operations	9,293	16,968	29,927	54,053
Interest income		6	35	51
Interest expense	(538)	(254)	(1,099)	(500)
Other income (expense) — net	(758)	890	(555)	(261)
Income before income tax provision	7,997	17,610	28,308	53,343
Depreciation and amortization	9,082	8,624	27,318	25,788
Activated Carbon and Service
Segment Information
Net Sales	112,504	121,330	339,861	367,644
Income (loss) from operations	9,669	18,054	31,328	55,696
Depreciation and amortization	8,586	7,954	25,630	23,461
Equipment
Segment Information
Net Sales	9,784	9,659	30,094	30,003
Income (loss) from operations	(543)	(1,278)	(2,390)	(2,680)
Depreciation and amortization	357	514	1,246	1,864
Consumer
Segment Information
Net Sales	1,682	1,987	6,811	6,484
Income (loss) from operations	167	192	989	1,037
Depreciation and amortization	$ 139	$ 156	$ 442	$ 463