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

Name:	ida_AuthorizedRateOfReturnInRateCase
Namespace Prefix:	ida
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

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

+ Details

Name:	ida_AuthorizedReturnOnEquityInRateCaseMaximum
Namespace Prefix:	ida
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

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

+ Details

Name:	ida_AuthorizedReturnOnEquityInRateCaseMinimum
Namespace Prefix:	ida
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The base deferral amount to be collected in rates as a result of, or requested in, a rate filing.

+ Details

Name:	ida_BaseDeferralAmountToBeCollected
Namespace Prefix:	ida
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount of forecasted demand response incentive payments that were included in the rate filing.

+ Details

Name:	ida_DemandResponseIncentivePaymentsIncludedInRateFiling
Namespace Prefix:	ida
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The existing carrying charge, expressed as an intererest rate, on the existing energy efficiency rider balance.

+ Details

Name:	ida_ExistingInterestRateOnEnergyEfficiencyRiderBalance
Namespace Prefix:	ida
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

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

+ Details

Name:	ida_IncreaseDecreaseInRates
Namespace Prefix:	ida
Data Type:	xbrli:monetaryItemType
Balance Type:	na
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.

+ Details

Name:	ida_InvestmentTaxCreditsMaximumInOneYearInRateCase
Namespace Prefix:	ida
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.

+ Details

Name:	ida_InvestmentTaxCreditsMaximumInRateCase
Namespace Prefix:	ida
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The load change adjustment rate is an element of the rate mechanism that recognizes the power supply expenses recovered through base rates change as loads increase or decrease. Rate is per megawatt-hour. This tag can also represent the open access same time draft rate, which is stated in kW/yr.

+ Details

Name:	ida_LoadChangeAdjustmentRateOrOpenAccessSameTimeDraftRate
Namespace Prefix:	ida
Data Type:	us-types:perUnitItemType
Balance Type:	na
Period Type:	instant

- Definition

The total percentage increase or (decrease) in rates, whether approved or requested, as a result of the rate case.

+ Details

Name:	ida_PercentageIncreaseDecreaseInRates
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 maximum authorized rate of return in the rate case.

+ Details

Name:	ida_PercentageToBeSharedWithCustomers
Namespace Prefix:	ida
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Power Purchased from PURPA Projects Included in Rate Case

+ Details

Name:	ida_PowerPurchasedFromPurpaProjectsIncludedInRateCase
Namespace Prefix:	ida
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Rate Case [Line Items]

+ Details

Name:	ida_RateCaseLineItems
Namespace Prefix:	ida
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Total retail rate base contemplated in the rate case.

+ Details

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

- Definition

The increase in the fair value of plan assets from contributions made by the employer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 5

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (b)(3)

-URI http://asc.fasb.org/extlink&oid=6962843&loc=d3e1928-114920

+ Details

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Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The amount for the individual regulatory asset as itemized in a table of regulatory assets as of the end of the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 71

-Paragraph 9, 10

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 980

-SubTopic 340

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6499975&loc=d3e44250-110382

+ Details

Name:	us-gaap_RegulatoryAssets
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- 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 Statement of Financial Accounting Standard (FAS)

-Number 71

-Paragraph 11

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

Name:	us-gaap_RegulatoryLiabilities
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
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Period Type:	instant

REGULATORY MATTERS: Level 4 (Details) (USD $)									12 Months Ended
REGULATORY MATTERS: Level 4 (Details) (USD $)	Sep. 23, 2011 Current Rate Case Idaho	Jun. 01, 2011 Current Rate Case Idaho	Nov. 02, 2011 Settlement Agreement and Sharing Mechanism	Sep. 30, 2011 Settlement Agreement and Sharing Mechanism	Jan. 13, 2010 Settlement Agreement and Sharing Mechanism	Sep. 30, 2011 Idaho Power Cost Adjustment	May 31, 2011 Idaho Load Change Adjustment	Sep. 30, 2011 Idaho Fixed Cost Adjustment	Dec. 31, 2010 Idaho Pension Recovery	Sep. 30, 2011 Idaho Pension Recovery	Sep. 30, 2011 Energy Efficiency and Demand Response Programs	Sep. 30, 2011 Transmission Rate Refunds and Shortfall Filing	Sep. 30, 2011 Current Rate Case Oregon	Oct. 20, 2011 Oregon Power Cost Adjustment	Sep. 30, 2011 Oregon Power Cost Adjustment	Sep. 30, 2011 Oregon Open Access Same Time Information System	Jun. 30, 2011 Oregon Open Access Same Time Information System
Rate Case
Increase (Decrease) in Rates	$ 34,000,000	$ 82,600,000				$ (40,400,000)		$ 3,000,000		$ 17,100,000	$ 42,000,000	$ 13,300,000	$ 5,800,000	$ 1,400,000	$ (900,000)	$ 107,000,000
Percentage Increase (Decrease) in Rates	4.07%	9.90%											14.70%
Authorized Return on Equity in Rate Case, Minimum		10.50%	9.50%		9.50%								10.50%
Investment Tax Credits, Maximum, in Rate Case			45,000,000
Investment Tax Credits Maximum in one Year in Rate Case			25,000,000
Authorized Return on Equity in Rate Case, Maximum			10.00%		10.50%
Regulatory Liabilities				18,100,000
Percentage to be Shared with Customers			50.00%		50.00%
Authorized Rate of Return in Rate Case	7.86%	8.17%											8.17%
Total Retail Rate Base	2,400,000,000												121,900,000
Load Change Adjustment Rate or Open Access Same Time Draft Rate	18.16	19.28					19.67									19.79	19.60
Demand Response Incentive Payments Included in Rate Filing	11,300,000					10,000,000
Power Purchased from PURPA Projects Included in Rate Case	23,000,000
Defined Benefit Plan, Contributions by Employer									60,000,000
Existing Interest Rate on Energy Efficiency Rider Balance											1.00%
Regulatory Assets										5,400,000		4,700,000
Base Deferral Amount to be Collected												$ 2,100,000