Segment Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013 Item	Jun. 30, 2012	Dec. 31, 2012
Segment Information
Number of reportable segments			3
Segment Information
Net Sales	$ 140,432	$ 148,403	$ 275,472	$ 285,011
Income (loss) from operations before depreciation, amortization, and restructuring	27,524	23,027	49,221	41,710
Depreciation and amortization	7,305	6,442	14,052	12,955
Income from operations before restructuring	20,219	16,585	35,169	28,755
Restructuring (Note 1)	18		42
Interest income	12	17	136	29
Interest expense	(129)		(306)	(19)
Other expense-net	(341)	(513)	(1,169)	(764)
Income before income tax provision	19,779	16,089	33,872	28,001
Total assets	574,589		574,589		577,769
Activated Carbon and Service
Segment Information
Net Sales	124,009	126,353	242,906	243,590
Income (loss) from operations before depreciation, amortization, and restructuring	27,706	20,526	48,605	37,829
Depreciation and amortization	6,353	5,650	12,261	11,423
Restructuring (Note 1)			42
Total assets	515,524		515,524		510,550
Equipment
Segment Information
Net Sales	14,302	19,887	28,210	36,005
Income (loss) from operations before depreciation, amortization, and restructuring	(624)	1,999	(231)	2,531
Depreciation and amortization	789	632	1,466	1,213
Total assets	52,506		52,506		60,191
Consumer
Segment Information
Net Sales	2,121	2,163	4,356	5,416
Income (loss) from operations before depreciation, amortization, and restructuring	442	502	847	1,350
Depreciation and amortization	163	160	325	319
Total assets	$ 6,559		$ 6,559		$ 7,028