Energy Purchase Contracts (Future Contractual Commitments For Power Resources And Natural Gas Resources) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014
Energy Purchase Contracts [Line Items]
2015	$ 360,358
2016	265,759
2017	201,803
2018	185,833
2019	174,636
Thereafter	1,316,706
Total	2,505,095
Power Resources [Member]
Energy Purchase Contracts [Line Items]
2015	277,474
2016	209,255
2017	144,424
2018	132,897
2019	125,332
Thereafter	860,731
Total	1,750,113
Natural Gas Resources [Member]
Energy Purchase Contracts [Line Items]
2015	82,884
2016	56,504
2017	57,379
2018	52,936
2019	49,304
Thereafter	455,975
Total	754,982
Generation Transmission And Distribution Facilities [Member]
Energy Purchase Contracts [Line Items]
2015	29,133
2016	35,692
2017	28,189
2018	25,659
2019	28,969
Thereafter	193,734
Total	$ 341,376

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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. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ 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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Amount of the fixed and determinable portion of the unrecorded unconditional purchase obligation maturing in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

+ Details

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- Definition

Amount of the fixed and determinable portion of the unrecorded unconditional purchase obligation maturing in the fourth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ 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. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

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Amount of the fixed and determinable portion of the unrecorded unconditional purchase obligation maturing in the third fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

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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

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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. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

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