Summary of Significant Accounting Policies (Details)	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Revenue by segment
Percentage of revenue by segment (in hundredths)	100.00%	[1]	100.00%	[1]	100.00%	[1]
Minerals and materials [Member]
Revenue by segment
Percentage of revenue by segment (in hundredths)	51.00%	[1]	50.00%	[1]	49.00%	[1]
Environmental [Member]
Revenue by segment
Percentage of revenue by segment (in hundredths)	27.00%	[1]	27.00%	[1]	29.00%	[1]
Oilfield services [Member]
Revenue by segment
Percentage of revenue by segment (in hundredths)	21.00%	[1]	19.00%	[1]	17.00%	[1]
Transportation [Member]
Revenue by segment
Percentage of revenue by segment (in hundredths)	6.00%	[1]	6.00%	[1]	7.00%	[1]
Intersegment sales [Member]
Revenue by segment
Percentage of revenue by segment (in hundredths)	(5.00%)	[1]	(2.00%)	[1]	(2.00%)	[1]

[1] Restated