Environmental and Legal Contingencies (Details 4) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2013 plaintiffs
Schumacher [Member]
Loss Contingencies [Line Items]
Loss Contingency, Number of Plaintiffs	92
Potential exposure of increase to defined benefit plan obligation	$ 3.0
Loss Contingency, Estimate of Possible Pre-Judgment Interest	1.0
Patrick [Member]
Loss Contingencies [Line Items]
Potential exposure of increase to defined benefit plan obligation	28.9
Consolidation Coal [Member]
Loss Contingencies [Line Items]
Loss Contingency, Damages Sought, Value	30.0
Loss Contingency Damages Sought Value Codefendant	$ 20.0

The value (monetary amount) of the award the plaintiff seeks in the legal matter.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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Reference 3: http://www.xbrl.org/2003/role/presentationRef

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

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Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 5

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 5

-Paragraph 10

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 5

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

- Definition

The estimated maximum amount of possible loss from the contingency.

+ References+ Details