Commitments and Contingencies, Fuel Contracts (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012
Coal [Member]
Fuel Contracts [Abstract]
2013	$ 317.3
2014	236.3
2015	196.8
2016	50.3
2017	40.9
Thereafter	0
Total	841.6
Natural Gas Supply [Member]
Fuel Contracts [Abstract]
2013	45.1
2014	12.0
2015	0
2016	0
2017	0
Thereafter	0
Total	57.1
Natural Gas Storage and Transportation [Member]
Fuel Contracts [Abstract]
2013	27.7
2014	23.5
2015	22.1
2016	22.1
2017	21.3
Thereafter	112.1
Total	$ 228.8

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The remaining amount of the fixed and determinable portion of an unrecorded unconditional purchase obligation to be paid in more than four and within five years from the balance sheet date.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 47

-Paragraph 7

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 440

-SubTopic 10

-Section 50

-Paragraph 4

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6394976&loc=d3e25336-109308

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- Definition

The remaining amount of the fixed and determinable portion of an unrecorded unconditional purchase obligation to be paid within one year of the balance sheet date.

+ References

+ Details

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- Definition

The remaining amount of the fixed and determinable portion of an unrecorded unconditional purchase obligation to be paid in more than three and within four years from the balance sheet date.

+ References

+ Details

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- Definition

The remaining amount of the fixed and determinable portion of an unrecorded unconditional purchase obligation to be paid in more than one and within two years from the balance sheet date.

+ References

+ Details

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- Definition

The remaining amount of the fixed and determinable portion of an unrecorded unconditional purchase obligation to be paid in more than two and within three years from the balance sheet date.

+ References

+ Details

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- Definition

The amount of the fixed and determinable portion of an unrecorded unconditional purchase obligation as of the balance sheet date.

+ References

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- Definition

The remaining amount of the fixed and determinable portion of an unrecorded unconditional purchase obligation to be paid after five years from the balance sheet date.

+ References

No definition available.

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