Fair Value Assumptions, Escalation Factor

No definition available.

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- Definition

Fair Value Assumptions, Operation And Maintenance Charges

+ References

No definition available.

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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.

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- Definition

Fair value, after the 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 not subject to a master netting arrangement and not elected to be offset.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=51825145&loc=SL20226008-175313

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=73719730&loc=d3e13495-108611

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

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-Subparagraph (a)
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Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 45
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41271-113958

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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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

Agreed upon price for the exchange of the underlying asset.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)
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- Definition

Measure of dispersion, in percentage terms (for instance, the standard deviation or variance), for a given stock price.

+ References

+ Details

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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) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2017 USD ($) $ / MWH MMBTU MWh $ / shares $ / MmBtu	Dec. 31, 2016 USD ($)
Power Option Agreement [Member] \| Black Scholes Merton [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Assumptions, Expected Volatility Rate	20.00%
Minimum [Member] \| Power Exchange Agreements [Member] \| Surrogate Facility Pricing [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Operation and Maintenance Charges	33.59
Transaction/Delivery Volumes \| MWh	396,984
Minimum [Member] \| Power Option Agreement [Member] \| Black Scholes Merton [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Transaction/Delivery Volumes \| MWh	125,837
Maximum [Member] \| Power Exchange Agreements [Member] \| Surrogate Facility Pricing [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Operation and Maintenance Charges	49.15
Transaction/Delivery Volumes \| MWh	396,984
Maximum [Member] \| Power Option Agreement [Member] \| Black Scholes Merton [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Transaction/Delivery Volumes \| MWh	285,979
Average [Member] \| Power Exchange Agreements [Member] \| Surrogate Facility Pricing [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Operation and Maintenance Charges	39.22
Fair Value, Measurements, Recurring [Member] \| Power Exchange Agreements [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Derivative Liability \| $	$ (14,419)	$ (13,449)
Fair Value, Measurements, Recurring [Member] \| Power Option Agreement [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Derivative Liability \| $	(266)	(76)
Fair Value, Measurements, Recurring [Member] \| Natural Gas Exchange Agreements [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Derivative Liability \| $	$ (4,278)	$ (5,885)
WASHINGTON \| Average [Member] \| Power Exchange Agreements [Member] \| Surrogate Facility Pricing [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Operation and Maintenance Charges	44.33
IDAHO \| Average [Member] \| Power Exchange Agreements [Member] \| Surrogate Facility Pricing [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Operation and Maintenance Charges	39.22
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, Forward Price \| $ / MmBtu	1.67
Transaction/Delivery Volumes \| MMBTU	60,000
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, Forward Price \| $ / MmBtu	3.50
Transaction/Delivery Volumes \| MMBTU	310,000
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, Forward Price \| $ / MmBtu	1.65
Transaction/Delivery Volumes \| MMBTU	115,000
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, Forward Price \| $ / MmBtu	2.83
Transaction/Delivery Volumes \| MMBTU	310,000
2017 \| Power Option Agreement [Member] \| Black Scholes Merton [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Assumptions, Exercise Price \| $ / shares	$ 50.43
2017 to 2019 [Member] \| Power Exchange Agreements [Member] \| Surrogate Facility Pricing [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Escalation Factor	3.00%
2018 \| Power Option Agreement [Member] \| Black Scholes Merton [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Assumptions, Exercise Price \| $ / shares	$ 35.30