Escalation Factor

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- Definition

Fair Value Assumptions, Average Operation And Maintenance Charges

+ References

No definition available.

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- Definition

Operation And Maintenance Charges

+ References

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- Definition

Fair value, before effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 20
-Section 50
-Paragraph 4D
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=82924980&loc=SL51823488-111719

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4B
-Subparagraph (a),(c)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624163-113959

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=82849420&loc=SL20226000-175313

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- Definition

The forward price on the price risk forward or futures contract, such as a gas futures contract.

+ References

No definition available.

+ Details

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- Definition

Nominal energy measure used to calculate payments on a derivative instrument.

+ References

No definition available.

+ Details

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- Definition

The strike price on the price risk option contract such as a put option or a call option.

+ References

No definition available.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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Fair Value (Quantitative Information) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) $ / MWH MMBTU MWh $ / MmBtu	Dec. 31, 2016 USD ($)
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Liability \| $	$ (161,467)	$ (150,381)
Power Exchange Agreements [Member] \| Surrogate Facility Pricing [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Assumptions, Average Operation And Maintenance Charges	41.95
Minimum [Member] \| Commodity Option [Member] \| Black Scholes Merton [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Derivative, Nonmonetary Notional Amount, Energy Measure \| MWh	94,221
Minimum [Member] \| Power Exchange Agreements [Member] \| Surrogate Facility Pricing [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Operation And Maintenance Charges	38.87
Derivative, Nonmonetary Notional Amount, Energy Measure \| MWh	256,663
Maximum [Member] \| Commodity Option [Member] \| Black Scholes Merton [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Derivative, Nonmonetary Notional Amount, Energy Measure \| MWh	190,339
Maximum [Member] \| Power Exchange Agreements [Member] \| Surrogate Facility Pricing [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Operation And Maintenance Charges	45.20
Derivative, Nonmonetary Notional Amount, Energy Measure \| MWh	396,984
Fair Value, Measurements, Recurring [Member] \| Commodity Option [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Liability \| $	$ (19)
Fair Value, Measurements, Recurring [Member] \| Power Exchange Agreements [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Liability \| $	(13,245)
Fair Value, Measurements, Recurring [Member] \| Natural Gas Exchange Agreements [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Liability \| $	$ (3,164)
Sales [Member] \| Minimum [Member] \| Natural Gas Exchange Agreements [Member] \| Internally Derived Weighted Average Cost Of Gas [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Derivative, Nonmonetary Notional Amount, Energy Measure \| MMBTU	60,000
Derivative, Forward Price \| $ / MmBtu	1.56
Sales [Member] \| Maximum [Member] \| Natural Gas Exchange Agreements [Member] \| Internally Derived Weighted Average Cost Of Gas [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Derivative, Nonmonetary Notional Amount, Energy Measure \| MMBTU	310,000
Derivative, Forward Price \| $ / MmBtu	2.98
Purchase [Member] \| Minimum [Member] \| Natural Gas Exchange Agreements [Member] \| Internally Derived Weighted Average Cost Of Gas [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Derivative, Nonmonetary Notional Amount, Energy Measure \| MMBTU	115,000
Derivative, Forward Price \| $ / MmBtu	1.60
Purchase [Member] \| Maximum [Member] \| Natural Gas Exchange Agreements [Member] \| Internally Derived Weighted Average Cost Of Gas [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Derivative, Nonmonetary Notional Amount, Energy Measure \| MMBTU	310,000
Derivative, Forward Price \| $ / MmBtu	2.07
Two Thousand Seventeen To Two Thousand Nineteen [Member] \| Power Exchange Agreements [Member] \| Surrogate Facility Pricing [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Escalation Factor	5.00%
2018 \| Minimum [Member] \| Commodity Option [Member] \| Black Scholes Merton [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Derivative, Price Risk Option Strike Price	36.64
2018 \| Maximum [Member] \| Commodity Option [Member] \| Black Scholes Merton [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Derivative, Price Risk Option Strike Price	42.51