Summary of Significant Accounting Policies (Details)	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Revenue by segment
Percentage of revenue by segment	100.00%	100.00%	100.00%
Minerals and Materials [Member]
Revenue by segment
Percentage of revenue by segment	51.00%	51.00%	49.00%
Environmental [Member]
Revenue by segment
Percentage of revenue by segment	26.00%	26.00%	29.00%
Oilfield Services [Member]
Revenue by segment
Percentage of revenue by segment	21.00%	18.00%	17.00%
Transportation [Member]
Revenue by segment
Percentage of revenue by segment	6.00%	6.00%	7.00%
Intersegment sales [Member]
Revenue by segment
Percentage of revenue by segment	(4.00%)	(1.00%)	(2.00%)