Segment, Geographic, and Market Information (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Segment, Geographic, and Market Information [Abstract]
Number of operating segments	5
Segment disclosure
Net sales	$ 943,796	[1]	$ 826,277	[1]	$ 687,485	[1]
Operating profit (loss)	86,086	[1]	69,012	[1]	49,344	[1]
Assets	849,142	[1]	807,255	[1]	746,835	[1]
Depreciation, depletion, and amortization	42,132	[1]	36,342	[1]	36,731	[1]
Capital expenditures	61,029	[1]	47,305	[1]	60,418	[1]
Research and development expenses	9,079	[1]	9,231	[1]	8,657	[1]
Minerals and Materials [Member]
Segment disclosure
Net sales	476,700	[1]	416,495	[1]	336,272	[1]
Operating profit (loss)	67,144	[1]	53,549	[1]	33,693	[1]
Assets	430,832	[1]	410,401	[1]	398,280	[1]
Depreciation, depletion, and amortization	20,639	[1]	17,202	[1]	16,813	[1]
Capital expenditures	27,306	[1]	29,700	[1]	35,659	[1]
Research and development expenses	6,488	[1]	5,913	[1]	5,344	[1]
Environmental [Member]
Segment disclosure
Net sales	251,907	[1]	225,544	[1]	202,511	[1]
Operating profit (loss)	17,349	[1]	20,447	[1]	23,924	[1]
Assets	159,365	[1]	160,969	[1]	150,237	[1]
Depreciation, depletion, and amortization	5,389	[1]	5,352	[1]	6,219	[1]
Capital expenditures	8,343	[1]	2,557	[1]	2,325	[1]
Research and development expenses	2,311	[1]	2,284	[1]	2,339	[1]
Oilfield Services [Member]
Segment disclosure
Net sales	194,735	[1]	153,550	[1]	119,821	[1]
Operating profit (loss)	21,226	[1]	13,654	[1]	12,261	[1]
Assets	194,708	[1]	172,521	[1]	146,161	[1]
Depreciation, depletion, and amortization	13,363	[1]	11,888	[1]	11,901	[1]
Capital expenditures	23,097	[1]	13,249	[1]	11,095	[1]
Research and development expenses	238	[1]	697	[1]	659	[1]
Transportation [Member]
Segment disclosure
Net sales	54,113	[1]	52,225	[1]	46,642	[1]
Operating profit (loss)	2,241	[1]	2,430	[1]	2,163	[1]
Assets	3,912	[1]	3,977	[1]	3,494	[1]
Depreciation, depletion, and amortization	76	[1]	46	[1]	38	[1]
Capital expenditures	198	[1]	92	[1]	39	[1]
Intersegment Sales [Member]
Segment disclosure
Net sales	(33,659)	[1]	(21,537)	[1]	(17,761)	[1]
Corporate [Member]
Segment disclosure
Operating profit (loss)	(21,874)	[1]	(21,068)	[1]	(22,697)	[1]
Assets	60,325	[1]	59,387	[1]	48,663	[1]
Depreciation, depletion, and amortization	2,665	[1]	1,854	[1]	1,760	[1]
Capital expenditures	2,085	[1]	1,707	[1]	11,300	[1]
Research and development expenses	$ 42	[1]	$ 337	[1]	$ 315	[1]

[1] Restated