Business Segment Information (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2011
Segment disclosure
Net sales	$ 235.8	$ 217.8
Operating profit (loss)	21.5	18.6
Assets	850.1	842.7	842.7	[1]
Depreciation, depletion, and amortization	10.6	9.4
Capital expenditures	16.6	10.4
Research and development (income) expense	2.5	1.9
Minerals and materials [Member]
Segment disclosure
Net sales	125.5	115.9
Operating profit (loss)	21.6	16.1
Assets	425.2	422.1
Depreciation, depletion, and amortization	4.6	4.5
Capital expenditures	6.5	2.8
Research and development (income) expense	1.7	1.6
Environmental [Member]
Segment disclosure
Net sales	51.1	51.7
Operating profit (loss)	0.9	2.4
Assets	166.6	161.4
Depreciation, depletion, and amortization	1.4	1.3
Capital expenditures	2.6	0.7
Research and development (income) expense	0.6	0.5
Oilfield services [Member]
Segment disclosure
Net sales	55.3	44.7
Operating profit (loss)	4.8	4.9
Assets	189.6	194.4
Depreciation, depletion, and amortization	4.0	3.0
Capital expenditures	6.0	6.4
Research and development (income) expense	0.1
Transportation [Member]
Segment disclosure
Net sales	11.1	12.7
Operating profit (loss)	0.2	0.5
Assets	3.9	3.9
Depreciation, depletion, and amortization
Capital expenditures
Intersegment sales [Member]
Segment disclosure
Net sales	(7.2)	(7.2)
Corporate [Member]
Segment disclosure
Operating profit (loss)	(6.0)	(5.3)
Assets	64.8	60.9
Depreciation, depletion, and amortization	0.6	0.6
Capital expenditures	1.5	0.5
Research and development (income) expense	$ 0.1	$ (0.2)

[1] *Condensed from audited financial statements.