Commitments and Contingencies, Fuel Contracts (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013
Coal [Member]
Fuel Contracts [Abstract]
2014	$ 330.3
2015	265.4
2016	232.2
2017	153.8
2018	42.5
Thereafter	424.7
Total	1,448.9
Natural Gas Supply [Member]
Fuel Contracts [Abstract]
2014	384.3
2015	228.0
2016	225.6
2017	222.1
2018	278.4
Thereafter	1,211.1
Total	2,549.5
Natural Gas Storage and Transportation [Member]
Fuel Contracts [Abstract]
2014	137.2
2015	136.5
2016	77.1
2017	50.9
2018	50.8
Thereafter	854.4
Total	$ 1,306.9

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Amount of the fixed and determinable portion of the unrecorded unconditional purchase obligation maturing in the fifth fiscal year following the latest fiscal year.

+ References

Reference 1: 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

+ Details

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- Definition

Amount of the fixed and determinable portion of the unrecorded unconditional purchase obligation maturing in the next fiscal year following the latest fiscal year.

+ References

+ Details

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- Definition

Amount of the fixed and determinable portion of the unrecorded unconditional purchase obligation maturing in the four fiscal year following the latest fiscal year.

+ References

+ Details

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- Definition

Amount of the fixed and determinable portion of the unrecorded unconditional purchase obligation maturing in the second fiscal year following the latest fiscal year.

+ References

+ Details

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- Definition

Amount of the fixed and determinable portion of the unrecorded unconditional purchase obligation maturing in the third fiscal year following the latest fiscal year.

+ References

+ Details

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- Definition

Amount of the unrecorded obligation to transfer funds in the future for fixed or minimum amounts or quantities of goods or services at fixed or minimum prices (for example, as in take-or-pay contracts or throughput contracts).

+ References

+ Details

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- Definition

Amount of the fixed and determinable portion of the unrecorded unconditional purchase obligation maturing after the fifth fiscal year following the latest fiscal year.

+ References

+ Details

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