Summary of Significant Accounting Policies (Tables)

6 Months Ended

Jun. 30, 2012

Summary of Significant Accounting Policies / Additional Balance Sheet Information [Abstract]

Revenue by segment

	Six Months Ended June 30,
	2012	2011
Minerals and materials	52%	51%
Environmental	23%	27%
Oilfield services	24%	20%
Transportation	5%	6%
Intersegment sales	-4%	-4%
	100%	100%