Annual fixed cost adjustment mechanism deferral amount, whether approved or requested.

No definition available.

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- Definition

The authorized rate of return, whether requested or approved, in the rate case.

+ References

No definition available.

+ Details

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Namespace Prefix:	ida_
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- Definition

The maximum authorized return on equity, whether requested or approved, in the rate case.

+ References

No definition available.

+ Details

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Namespace Prefix:	ida_
Data Type:	num:percentItemType
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Period Type:	instant

- Definition

Authorized Return on Equity in Rate Case, Mid-point

+ References

No definition available.

+ Details

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Namespace Prefix:	ida_
Data Type:	num:percentItemType
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Period Type:	instant

- Definition

The minimum authorized return on equity, whether requested or approved, in the rate case.

+ References

No definition available.

+ Details

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Namespace Prefix:	ida_
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Period Type:	instant

- Definition

Total amount of increase or (decrease) in rate base, whether approved or requested, as a result of the related rate case or application.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The maximum amount, whether proposed or approved, of additional investment tax credits that are allowed in the rate case in a given year that are computed by applying the domestic federal statutory income tax rates to pretax income from continuing operations attributable to investment tax credits generated or utilized under enacted tax laws during the period.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The maximum amount, whether proposed or approved, of additional investment tax credits that are allowed in the rate case that are computed by applying the domestic federal statutory income tax rates to pretax income from continuing operations attributable to investment tax credits generated or utilized under enacted tax laws during the period.

+ References

No definition available.

+ Details

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Namespace Prefix:	ida_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Percentage of earnings to be Shared with Customers, though additional pension expense as a reduction to the pension regulatory asset balancing account, that is above the maximum authorized rate of return in the rate case.

+ References

No definition available.

+ Details

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Namespace Prefix:	ida_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage of earnings to be Shared with Customers, though a rate reduction effective at the time of the subsequent year's power cost adjustment, that is above the maximum authorized rate of return in the rate case.

+ References

No definition available.

+ Details

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Namespace Prefix:	ida_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage of earnings to be Shared with Customers that is above the applicable authorized rate of return in the rate case.

+ References

No definition available.

+ Details

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Namespace Prefix:	ida_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage of earnings to be Shared with the Entity that is above the applicable authorized rate of return in the rate case.

+ References

No definition available.

+ Details

Name:	ida_PercentageToBeSharedWithEntity
Namespace Prefix:	ida_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Rate Case [Line Items]

+ References

No definition available.

+ Details

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Namespace Prefix:	ida_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Total retail rate base contemplated in the rate case.

+ References

No definition available.

+ Details

Name:	ida_TotalRetailRateBase
Namespace Prefix:	ida_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

ValmySettlementStipulationRateIncreaseAfterTaxNetIncomeEffect

+ References

No definition available.

+ Details

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Namespace Prefix:	ida_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to investment tax credit.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 13
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32698-109319

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of public utility's approved rate increase (decrease) by regulatory agency.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Percentage of public utility's approved return on equity.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount for the individual regulatory liability as itemized in a table of regulatory liabilities as of the end of the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 980
-SubTopic 405
-Section 25
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6500807&loc=d3e48068-110394

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

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Namespace Prefix:
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Balance Type:
Period Type:

- Details

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Balance Type:
Period Type:

- Details

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Period Type:

- Details

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Namespace Prefix:
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Balance Type:
Period Type:

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

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Period Type:

- Details

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REGULATORY MATTERS: Level 4 (Details) - USD ($) $ in Thousands								3 Months Ended	9 Months Ended		12 Months Ended
	Jul. 01, 2017	Jun. 01, 2017	Jun. 01, 2014	Oct. 01, 2012	Jul. 01, 2012	Mar. 01, 2012	Jan. 01, 2012	Sep. 30, 2017	Sep. 30, 2017	Sep. 30, 2016	May 31, 2018	May 31, 2017	Dec. 31, 2016	Jun. 01, 2016	Jun. 01, 2015	Oct. 30, 2014
Rate Case
Additional ADITC amortization									$ 0	$ 1,500
Idaho Power Company
Rate Case
Additional ADITC amortization									0	1,500
Idaho and Oregon General Rate Cases and Base Rate Adjustments \| IDAHO
Rate Case
Authorized Rate of Return in Rate Case							7.86%
Total Retail Rate Base							$ 2,360,000
Approved Rate Increase (Decrease), Amount							$ 34,000
Idaho and Oregon General Rate Cases and Base Rate Adjustments \| OREGON
Rate Case
Authorized Rate of Return in Rate Case						7.757%
Approved Rate Increase (Decrease), Amount						$ 1,800
Public Utilities, Approved Return on Equity, Percentage						9.90%
Base rate adjustment request for potential Valmy closure [Member] [Member]
Rate Case
ValmySettlementStipulationRateIncreaseAfterTaxNetIncomeEffect								$ 1,300	3,800
Base rate adjustment request for potential Valmy closure [Member] [Member] \| IDAHO
Rate Case
Approved Rate Increase (Decrease), Amount		$ 13,300
Base rate adjustment request for potential Valmy closure [Member] [Member] \| OREGON
Rate Case
Approved Rate Increase (Decrease), Amount	$ 1,100
Cost Recovery for Langley Gulch Power Plant \| IDAHO
Rate Case
Approved Rate Increase (Decrease), Amount					$ 58,100
Increase (Decrease) in Rate Base					$ 335,900
Cost Recovery for Langley Gulch Power Plant \| OREGON
Rate Case
Approved Rate Increase (Decrease), Amount				$ 3,000
Idaho Settlement Stipulation - Investment Tax Credits and Sharing Mechanism
Rate Case
Authorized Return on Equity in Rate Case, Minimum																9.50%
Authorized Return on Equity in Rate Case, Mid-point																10.00%
Authorized Return on Equity in Rate Case, Maximum																10.50%
Investment Tax Credits Maximum In One Year In Rate Case																$ 25,000
Investment Tax Credits, Maximum, in Rate Case																$ 45,000
Additional ADITC amortization									$ 0	$ 1,500
Percentage to be Shared with Customers																75.00%
Percentage to be Shared with Entity																25.00%
Percent To Be Shared With Customers, Power Cost Adjustment																50.00%
Percent To Be Shared With Customers, Pension Balancing																25.00%
Regulatory Liabilities													$ 3,200
Annual Power Cost Adjustment Mechanism Filing [Member]
Rate Case
Approved Rate Increase (Decrease), Amount			$ 106,000									$ 17,300
Regulatory Liabilities		13,000											$ 4,000
Annual Power Cost Adjustment Mechanism Filing [Member] \| IDAHO
Rate Case
Approved Rate Increase (Decrease), Amount			$ 99,000
Idaho Fixed Cost Adjustment Mechanism Annual Filing
Rate Case
Approved Rate Increase (Decrease), Amount												$ 11,200
Annual fixed cost adjustment mechanism deferral		$ 35,000												$ 28,100	$ 16,900
Scenario, Forecast [Member] \| Idaho Fixed Cost Adjustment Mechanism Annual Filing
Rate Case
Approved Rate Increase (Decrease), Amount											$ 6,900
Subsequent Event [Member] \| Annual Power Cost Adjustment Mechanism Filing [Member]
Rate Case
Approved Rate Increase (Decrease), Amount											$ 10,600