Income Taxes - Effective Income Tax Rate Reconciliation (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Effective Income Tax Rate Reconciliation [Abstract]
Provision for income taxes at U.S. statutory rates	$ 12.3	$ 29.5	$ 26.3
Percentage of Pretax Income, Provision for income taxes at U.S. statutory rates (in hundredths)	35.00%	35.00%	35.00%
Increase (decrease) in taxes resulting from [Abstract]
Percentage depletion	(5.9)	(5.0)	(4.9)
Percent of pretax income, Percentage depletion (in hundredths)	(16.70%)	(6.00%)	(6.50%)
State taxes, net of federal benefit	1.1	1.7	2.2
Percent of pretax income, State taxes, net of federal benefit (in hundredths)	3.00%	2.10%	2.90%
Foreign tax rates	1.2	(3.0)	(1.0)
Percent of pretax income, Foreign tax rates (in hundredths)	3.60%	(3.60%)	(1.40%)
Domestic manufacturing deduction	(1.2)	(1.6)	(0.8)
Percent of pretax income, domestic manufacturing deduction (in hundredths)	(3.30%)	(1.90%)	(1.10%)
Change in state tax rates	0.2	(1.9)	0
Percent of pretax income, Change in state tax rates (in hundredths)	0.50%	(2.20%)	0.00%
Foreign withholding tax	2.2	1.6	1.0
Percent of pretax income, foreign withholding tax (in hundredths)	6.20%	2.00%	1.30%
Foreign tax credits	(3.6)	(3.2)	(2.4)
Percent of pretax income, Foreign tax credits (in hundredths)	(10.30%)	(3.80%)	(3.10%)
Changes to valuation allowance	8.0	1.9	(0.2)
Percent of pretax income, Changes to valuation allowance (in hundredths)	22.70%	2.20%	(0.30%)
Sale of available-for-sale securities	(3.5)	0	0
Percent of pretax income, Tax from foreign disregarded entities (in hundredths)	(10.00%)	0.00%	0.00%
Other	0.2	3.3	0.6
Percent of pretax income, Other (in hundredths)	0.50%	3.90%	0.80%
Income tax expense (benefit), continuing operations, total	$ 11.0	$ 23.3	$ 20.8
Percent of pretax income, Effective tax rates related to income from continuing operations before income taxes (in hundredths)	31.20%	27.70%	27.60%