Goodwill and Intangible Assets (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010
Schedule of the balance of goodwill by segment and the activity occurring in the past two fiscal years
Balance at beginning of the period	$ 70,909	[1]	$ 71,156
Change in goodwill relating to:
Acquisitions			761
Sale of business	(156)
Foreign exchange translation	(1,244)		(1,008)
Total changes	(1,400)		(247)
Balance at ending of the period	69,509	[1]	70,909	[1]
Minerals and Materials [Member]
Schedule of the balance of goodwill by segment and the activity occurring in the past two fiscal years
Balance at beginning of the period	18,201		18,426
Change in goodwill relating to:
Acquisitions			0
Sale of business	0
Foreign exchange translation	(817)		(225)
Total changes	(817)		(225)
Balance at ending of the period	17,384		18,201
Environmental [Member]
Schedule of the balance of goodwill by segment and the activity occurring in the past two fiscal years
Balance at beginning of the period	21,740		21,762
Change in goodwill relating to:
Acquisitions			761
Sale of business	(156)
Foreign exchange translation	(427)		(783)
Total changes	(583)		(22)
Balance at ending of the period	21,157		21,740
Oilfield Services [Member]
Schedule of the balance of goodwill by segment and the activity occurring in the past two fiscal years
Balance at beginning of the period	30,968		30,968
Change in goodwill relating to:
Acquisitions			0
Sale of business	0
Foreign exchange translation	0		0
Total changes	0		0
Balance at ending of the period	$ 30,968		$ 30,968

[1] Restated