Income Taxes (Details 4) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Effective Income Tax Rate Reconciliation
Provision for income taxes at U.S. statutory rates	$ 29.5	$ 26.3	$ 21.2
Percentage of provision for income taxes at U.S. statutory rates (in hundredths)	35.00%	35.00%	35.00%
Increase (decrease) in taxes resulting from:
Percentage depletion	(5.0)	(4.9)	(3.9)
Percent of pretax income, Percentage depletion (in hundredths)	(6.00%)	(6.50%)	(6.40%)
State taxes, net of federal benefit	1.7	2.2	1.5
Percent of pretax income, State taxes, net of federal benefit (in hundredths)	2.10%	2.90%	2.60%
Foreign tax rates	(3.9)	(1.0)	(0.9)
Percent of pretax income, Foreign tax rates (in hundredths)	(4.60%)	(1.40%)	(1.50%)
Change in reserve for tax uncertainties	0	(0.7)	0.1
Percent of pretax income, Change in reserve for tax uncertainties (in hundredths)	0.00%	(0.90%)	0.10%
Domestic manufacturing deduction	(1.6)	(0.8)	(0.5)
Percent of pretax income, domestic manufacturing deduction (in hundredths)	(1.90%)	(1.10%)	(0.80%)
Change in state tax rates	(1.9)	0	(0.1)
Percent of pretax income, Change in state tax rates (in hundredths)	(2.20%)	0.00%	(0.20%)
Foreign witholding tax	1.6	1.0	0.6
Percent of pretax income, foreign witholding tax (in hundredths)	2.00%	1.30%	1.00%
Foreign tax credits	(3.2)	(2.4)	(2.2)
Percent of pretax income, Foreign tax credits (in hundredths)	(3.80%)	(3.10%)	(3.60%)
Changes to valuation allowance	1.9	(0.2)	3.4
Percent of pretax income, Changes to valuation allowance (in hundredths)	2.20%	(0.30%)	5.60%
Tax from foreign disregarded entities	0.4	0.3	1.4
Percent of pretax income, Tax from foreign disregarded entities (in hundredths)	0.50%	0.30%	2.20%
Other	3.8	1.0	(0.3)
Percent of pretax income, Other (in hundredths)	4.30%	1.40%	(0.60%)
Income tax expense (benefit), continuing operations, total	$ 23.3	$ 20.8	$ 20.3
Percent of pretax income, Effective tax rates related to income from continuing operations before income taxes (in hundredths)	27.60%	27.60%	33.40%