Energy Purchase Contracts (Future Contractual Commitments For Power Resources And Natural Gas Resources) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011
Energy Purchase Contracts [Line Items]
2012	$ 352,646
2013	260,324
2014	227,106
2015	188,816
2016	166,173
Thereafter	1,677,058
Total	2,872,123
Power Resources [Member]
Energy Purchase Contracts [Line Items]
2012	218,599
2013	157,401
2014	139,180
2015	116,184
2016	111,698
Thereafter	1,037,268
Total	1,780,330
Natural Gas Resources [Member]
Energy Purchase Contracts [Line Items]
2012	134,047
2013	102,923
2014	87,926
2015	72,632
2016	54,475
Thereafter	639,790
Total	1,091,793
Generation Transmission And Distribution Facilities [Member]
Energy Purchase Contracts [Line Items]
2012	29,103
2013	30,346
2014	30,891
2015	28,392
2016	32,528
Thereafter	246,503
Total	$ 397,763

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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

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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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