Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013 Item	Mar. 31, 2012	Dec. 31, 2012
Segment Information
Number of reportable segments	3
Segment Information
Net Sales	$ 135,040	$ 136,608
Income from operations before depreciation, amortization and restructuring	21,697	18,683
Depreciation and amortization	6,747	6,513
Income from operations before restructuring	14,950	12,170
Restructuring (Note 1)	24
Interest income	124	18
Interest expense	(177)	(25)
Other expense - net	(828)	(251)
Income before income tax provision	14,093	11,912
Total assets	572,897		577,769
Activated Carbon and Service
Segment Information
Net Sales	118,897	117,237
Income from operations before depreciation, amortization and restructuring	20,899	17,303
Depreciation and amortization	5,908	5,773
Restructuring (Note 1)	24
Total assets	508,568		510,550
Equipment
Segment Information
Net Sales	13,908	16,118
Income from operations before depreciation, amortization and restructuring	393	532
Depreciation and amortization	677	581
Total assets	58,413		60,191
Consumer
Segment Information
Net Sales	2,235	3,253
Income from operations before depreciation, amortization and restructuring	405	848
Depreciation and amortization	162	159
Total assets	$ 5,916		$ 7,028