Commitments and Contingencies (Piedmont) (Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended
Dec. 31, 2012	Sep. 30, 2008
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies, Maximum payout period, years	30 years
Piedmont, Florida [Member]
Loss Contingencies [Line Items]
Accrual for environmental loss contingencies	$ 20.1	$ 24.0
Years to complete environmental remediation (beginning in 2015)		15 years
Change in estimated exposure	0
Total anticipated exposure at this site		24.0
Segment Discontinued Operations Member \| Piedmont, Florida [Member]
Loss Contingencies [Line Items]
Pretax environmental expense		$ 24.0

Total costs accrued as of the balance sheet date for environmental loss contingencies.

+ References+ Details

The charge against earnings in the period for known or estimated future costs arising from requirements to perform environmental remediation activities.

+ References

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

-Publisher AICPA

-Name Statement of Position (SOP)

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Reference 2: http://www.xbrl.org/2003/role/presentationRef

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

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Emerging Issues Task Force (EITF)

-Number 90-8

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 Accounting Standards Codification

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

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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.

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