Business Segment Information (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended		12 Months Ended
	Jun. 30, 2012	Mar. 31, 2012	Jun. 30, 2011	Mar. 31, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Segment disclosure
Net sales	$ 257.4	$ 235.6	$ 243.1	$ 218.6	$ 493.0	$ 461.7	$ 943.8	$ 826.2	$ 688.5
Operating profit (loss)	31.0	21.3	21.0	19.3	52.3	40.3	87.1	69.2	50.0
Assets	869.0				869.0		850.6	807.8
Depreciation, depletion, and amortization	11.1		10.4		21.8	19.9
Capital expenditures	15.6		14.4		32.2	24.8
Research and development (income) expense	2.6		2.3		5.1	4.2
Minerals and materials [Member]
Segment disclosure
Net sales	131.1		118.3		256.3	234.1
Operating profit (loss)	22.5		13.5		44.0	29.5
Assets	436.9				436.9		431.1
Depreciation, depletion, and amortization	4.9		5.4		9.5	10.0
Capital expenditures	4.3		6.3		10.8	9.1
Research and development (income) expense	1.9		1.5		3.6	3.1
Environmental [Member]
Segment disclosure
Net sales	61.3		74.8		112.4	126.5
Operating profit (loss)	6.2		8.0		7.0	10.1
Assets	169.4				169.4		160.0
Depreciation, depletion, and amortization	1.3		1.3		2.7	2.6
Capital expenditures	3.7		1.1		6.3	1.8
Research and development (income) expense	0.6		0.6		1.2	1.1
Oilfield services [Member]
Segment disclosure
Net sales	61.1		45.1		116.4	90.7
Operating profit (loss)	7.7		3.7		12.5	9.5
Assets	197.7				197.7		194.7
Depreciation, depletion, and amortization	4.2		3.1		8.2	6.1
Capital expenditures	7.0		6.5		13.0	12.9
Research and development (income) expense	0.3		0.2		0.4	0.2
Transportation [Member]
Segment disclosure
Net sales	11.7		14.8		22.8	27.5
Operating profit (loss)	0.3		0.7		0.5	1.2
Assets	3.8				3.8		3.9
Depreciation, depletion, and amortization
Capital expenditures			0.2			0.2
Intersegment sales [Member]
Segment disclosure
Net sales	(7.8)		(9.9)		(14.9)	(17.1)
Corporate [Member]
Segment disclosure
Operating profit (loss)	(5.7)		(4.9)		(11.7)	(10.0)
Assets	61.2				61.2		60.9
Depreciation, depletion, and amortization	0.7		0.6		1.4	1.2
Capital expenditures	0.6		0.3		2.1	0.8
Research and development (income) expense	$ (0.2)				$ (0.1)	$ (0.2)