Energy Purchase Contracts (Future Contractual Commitments For Power Resources And Natural Gas Resources) (Details) $ in Thousands	Dec. 31, 2016 USD ($)
Energy Purchase Contracts [Line Items]
2017	$ 298,043
2018	252,310
2019	228,145
2020	151,218
2021	125,791
Thereafter	1,125,016
Total	2,180,523
Power Resources [Member]
Energy Purchase Contracts [Line Items]
2017	202,494
2018	187,080
2019	174,285
2020	109,878
2021	96,485
Thereafter	775,548
Total	1,545,770
Natural Gas Resources [Member]
Energy Purchase Contracts [Line Items]
2017	95,549
2018	65,230
2019	53,860
2020	41,340
2021	29,306
Thereafter	349,468
Total	634,753
Generation Transmission And Distribution Facilities [Member]
Energy Purchase Contracts [Line Items]
2017	33,922
2018	28,783
2019	32,549
2020	32,160
2021	27,019
Thereafter	189,000
Total	$ 343,433

Energy Purchase Contracts [Line Items]

No definition available.

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- Definition

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=73718637&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. 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

+ 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. 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 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

+ Details

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