Name:	xel_AmountsCurrentlyRecoveredInAutomaticRecoveryMechanismsIncludedInRequestedRateIncreaseDecreaseForNextYear
Namespace Prefix:	xel_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

The amount of the customers' share of Renewable Energy Credit trading margins netted against the renewable energy standard adjustment (RESA) regulatory asset balance.

No definition available.

Name:	xel_CustomersShareOfMarginsCreditedAgainstResaRegulatoryAssetBalance
Namespace Prefix:	xel_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

The first range of an earnings test in the entity's rate regulatory proceeding approved for implementation, filed with the applicable regulatory agency, in which customers and shareholders will share earnings above a rate of return on equity of 10.0%. The first range is greater than 10.0% and less than or equal to 10.2%.

No definition available.

Name:	xel_EarningsTestRoeRange1
Namespace Prefix:	xel_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

The second range of an earnings test in the entity's rate regulatory proceeding approved for implementation, filed with the applicable regulatory agency, in which customers and shareholders will share earnings above a rate of return on equity of 10.0%. The second range is greater than 10.2% and less than 10.5%.

No definition available.

Name:	xel_EarningsTestRoeRange2
Namespace Prefix:	xel_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

The third range of an earnings test in the entity's rate regulatory proceeding approved for implementation, filed with the applicable regulatory agency, in which customers and shareholders will share earnings above a rate of return on equity of 10.0%. The third range is greater than 10.5%.

No definition available.

Name:	xel_EarningsTestRoeRange3
Namespace Prefix:	xel_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

The entity's additional requested amount of the increase to existing rates for 2012, filed with the applicable regulatory agency.

No definition available.

Name:	xel_EntitysAdditionalRequestedRateIncreaseDecrease
Namespace Prefix:	xel_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

The adjustment to the entity's revised requested amount of increase (decrease) to existing rates related to depreciation expense, approved by the applicable regulatory agency.

No definition available.

Name:	xel_EntitysAdjustmentRelatedToDepreciation
Namespace Prefix:	xel_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

The amount of increase (decrease) to existing property taxes within the settlement agreement that will have deferred accounting treatment if approved by the applicable regulatory agency.

No definition available.

Name:	xel_EntitysAdjustmentRelatedToPropertyTaxes
Namespace Prefix:	xel_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

The entity's amortization period for incremental property taxes that will have deferred accounting treatment (2010-2011 historic test year property taxes) approved for implementation, filed with the applicable regulatory agency.

No definition available.

Name:	xel_EntitysAmortizationPeriodForDeferredIncrementalPropertyTaxes
Namespace Prefix:	xel_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

The ratio of equity to total capitalization (debt plus equity) used in the entity's original requested rate regulatory proceeding for 2011, approved by the applicable regulatory agency.

No definition available.

Name:	xel_EntitysApprovedEquityRatioPercent
Namespace Prefix:	xel_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

The entity's requested amount of increase (decrease) to existing rates for 2011, approved by the applicable regulatory agency.

No definition available.

Name:	xel_EntitysApprovedRateIncreaseDecreaseFor2011
Namespace Prefix:	xel_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

The entity's requested rate increase (decrease) to existing rates for 2012, approved by the applicable regulatory agency.

No definition available.

Name:	xel_EntitysApprovedRateIncreaseDecreaseFor2012
Namespace Prefix:	xel_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

The ratio of equity to total capitalization (debt plus equity) used in the entity's rate regulatory proceeding approved for implementation, filed with the applicable regulatory agency.

No definition available.

Name:	xel_EntitysEquityRatioPercentApprovedForImplementation
Namespace Prefix:	xel_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

The entity's implemented rate increase (decrease) to existing rates, approved by the applicable regulatory agency

No definition available.

Name:	xel_EntitysInterimRateIncreaseImplemented
Namespace Prefix:	xel_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

The entity's incremental property taxes in excess of amount that will have deferred accounting treatment (2010-2011 historic test year property taxes) approved for implementation, filed with the applicable regulatory agency.

No definition available.

Name:	xel_EntitysMinimumIncrementalPropertyTaxesToBeDeferred
Namespace Prefix:	xel_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

The entity's minimum net revenue requirements increases or decreases caused by changes in tax law, government mandates, or natural disasters which may be deferred or recovered through a modified rate adjustment, filed with the applicable regulatory agency.

No definition available.

Name:	xel_EntitysMinimumNetRevenueRequirementsIncreasesOrDecreases
Namespace Prefix:	xel_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

The entity's minimum percent of normalized base revenues in either 2012 or 2013 below 2011 actual levels adjusted to reflect the rate increases allowed for 2012 and 2013 which give the entity the right to an additional rate adjustment in the next year for 50 percent of the shortfall, filed with the applicable regulatory agency.

No definition available.

Name:	xel_EntitysMinimumPercentOfNormalizedBaseRevenuesBelowAdjustedActualLevels
Namespace Prefix:	xel_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

The ratio of equity to total capitalization (debt plus equity) used in the entity's original requested rate regulatory proceeding for 2011, filed with the applicable regulatory agency.

No definition available.

Name:	xel_EntitysOriginalRequestedEquityRatioPercent
Namespace Prefix:	xel_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

The ratio of equity to total capitalization (debt plus equity) used in the entity's original requested rate regulatory proceeding for 2012, filed with the applicable regulatory agency.

No definition available.

Name:	xel_EntitysOriginalRequestedEquityRatioPercentForNextYear
Namespace Prefix:	xel_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

The cost of debt originally requested by the entity in a rate case proceeding for 2012, filed with the applicable regulatory agency.

No definition available.

Name:	xel_EntitysOriginalRequestedPercentCostOfDebt
Namespace Prefix:	xel_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Rate of return on equity that the entity's original revenue increase requested represented through a rate case proceeding for 2011, filed with the applicable regulatory agency

No definition available.

Name:	xel_EntitysOriginalRequestedPercentReturnOnEquity
Namespace Prefix:	xel_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Rate of return on equity that the entity's original revenue increase requested represented through a rate case proceeding for 2012, filed with the applicable regulatory agency

No definition available.

Name:	xel_EntitysOriginalRequestedPercentReturnOnEquityForNextYear
Namespace Prefix:	xel_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

The entity's original requested amount of increase (decrease) to existing rates for 2011, filed with the applicable regulatory agency.

No definition available.

Name:	xel_EntitysOriginalRequestedRateIncreaseDecrease
Namespace Prefix:	xel_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

The entity's original requested amount of increase (decrease) to existing rates for 2012, filed with the applicable regulatory agency.

No definition available.

Name:	xel_EntitysOriginalRequestedRateIncreaseDecreaseForNextYear
Namespace Prefix:	xel_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

The entity's percent of shortfall which can be included in an additional rate adjustment in the next year, filed with the applicable regulatory agency.

No definition available.

Name:	xel_EntitysPercentOfShortfallWhichCanBeIncludedInAdditionalRateAdjustment
Namespace Prefix:	xel_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Rate of return on equity that the entity's revenue increase (decrease) approved for implementation represented through a rate case proceeding, filed with the applicable regulatory agency.

No definition available.

Name:	xel_EntitysPercentReturnOnEquityApprovedForImplementation
Namespace Prefix:	xel_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

The entity's requested value established on which the entity is allowed to earn a particular rate of return on operations for 2011, filed with the applicable regulatory agency.

No definition available.

Name:	xel_EntitysRateBaseInOriginalRequestedRateIncreaseDecrease
Namespace Prefix:	xel_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

The entity's requested value established on which the entity is allowed to earn a particular rate of return on operations for 2012, filed with the applicable regulatory agency.

No definition available.

Name:	xel_EntitysRateBaseInOriginalRequestedRateIncreaseDecreaseForNextYear
Namespace Prefix:	xel_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

The rate increase (decrease) approved for implementation in 2012, approved by the applicable regulatory agency.

No definition available.

Name:	xel_EntitysRateIncreaseApprovedForImplementationInCurrentYear
Namespace Prefix:	xel_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

The rate increase (decrease) approved for implementation in 2013, approved by the applicable regulatory agency.

No definition available.

Name:	xel_EntitysRateIncreaseApprovedForImplementationInNextYear
Namespace Prefix:	xel_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

The rate increase (decrease) approved for implementation in 2014, approved by the applicable regulatory agency.

No definition available.

Name:	xel_EntitysRateIncreaseApprovedForImplementationInTwoYears
Namespace Prefix:	xel_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

The entity's provision for revenue subject to refund for the period.

No definition available.

Name:	xel_EntitysRecordedProvisionForRevenueSubjectToRefund
Namespace Prefix:	xel_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

The entity's revised requested amount of increase (decrease) to interim rates for 2011, filed with the applicable regulatory agency.

No definition available.

Name:	xel_EntitysRevisedInterimRateIncreaseImplemented
Namespace Prefix:	xel_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Rate of return on equity that the entity's revised revenue increase requested represented through a rate case proceeding for 2011, filed with the applicable regulatory agency.

No definition available.

Name:	xel_EntitysRevisedRequestedPercentReturnOnEquity
Namespace Prefix:	xel_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

The entity's lower range of the rate of return on equity that the entity's revised revenue increase requested represented through a rate case proceeding for 2011, filed with the applicable regulatory agency.

No definition available.

Name:	xel_EntitysRevisedRequestedPercentReturnOnEquityLowerRange
Namespace Prefix:	xel_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

The entity's upper range of the rate of return on equity that the entity's revised revenue increase requested represented through a rate case proceeding for 2011, filed with the applicable regulatory agency.

No definition available.

Name:	xel_EntitysRevisedRequestedPercentReturnOnEquityUpperRange
Namespace Prefix:	xel_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

The entity's revised requested amount of increase (decrease) to existing rates for 2011, filed with the applicable regulatory agency.

No definition available.

Name:	xel_EntitysRevisedRequestedRateIncreaseDecrease
Namespace Prefix:	xel_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

The entity's revised requested rate increase (decrease) to existing rates for 2012, filed with the applicable regulatory agency.

No definition available.

Name:	xel_EntitysRevisedRequestedRateIncreaseDecreaseForNextYear
Namespace Prefix:	xel_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

The first amount of margins on hybrid Renewable Energy Credits (REC) trades to be shared approved by the applicable regulatory agency.

No definition available.

Name:	xel_FirstAmountOfMarginsOnHybridRecTradesToBeShared
Namespace Prefix:	xel_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

The percentage of margin associated with stand-alone Renewable Energy Credit transactions which will be shared beginning in 2011 as determined by the Colorado Public Utilities Commission.

No definition available.

Name:	xel_InitialPercentageOfMarginAssociatedWithStandAloneRecTransactions
Namespace Prefix:	xel_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

The maximum percentage of margin associated with stand-alone REC transactions which will be shared by 2014 as determined by the Colorado Public Utilities Commission.

No definition available.

Name:	xel_MaximumPercentageOfMarginAssociatedWithStandAloneRecTransactions
Namespace Prefix:	xel_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

The maximum rate of return on equity that an independent third party's revenue increase represented through a rate case proceeding for 2012, filed with the applicable regulatory agency.

No definition available.

Name:	xel_MaximumRecommendationForPercentReturnOnEquity
Namespace Prefix:	xel_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

The minimum rate of return on equity that an independent third party's revenue increase represented through a rate case proceeding for 2012, filed with the applicable regulatory agency.

No definition available.

Name:	xel_MinimumRecommendationForPercentReturnOnEquity
Namespace Prefix:	xel_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

The percentage increase in the entity's additional amount of increase (decrease) to existing rates for 2012, filed with the applicable regulatory agency.

No definition available.

Name:	xel_PercentageIncreaseInEntitysAdditionalRequestedRateIncrease
Namespace Prefix:	xel_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

The percentage increase in the entity's original requested amount of increase (decrease) for 2011 to existing rates, filed with the applicable regulatory agency.

No definition available.

Name:	xel_PercentageIncreaseInEntitysOriginalRequestedRateIncrease
Namespace Prefix:	xel_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

The percentage increase in the entity's revised requested amount of increase (decrease) for 2011 to existing rates, filed with the applicable regulatory agency.

No definition available.

Name:	xel_PercentageIncreaseInEntitysRevisedRequestedRateIncrease
Namespace Prefix:	xel_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

The percentage increase in the entity's revised requested amount of increase (decrease) for 2012 to existing rates, filed with the applicable regulatory agency.

No definition available.

Name:	xel_PercentageIncreaseInEntitysRevisedRequestedRateIncreaseForNextYear
Namespace Prefix:	xel_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

The percentage of margin associated with Colorado Renewable Energy Credits (REC) approved to be shared on the first $20 million of margins on hybrid REC trades.

No definition available.

Name:	xel_PercentageOfMarginOnHybridRecsApprovedForFirst20MillionOfMargins
Namespace Prefix:	xel_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

The percentage of margin associated with Colorado Renewable Energy Credits (REC) approved to be shared in excess of $20 million of margins on hybrid REC trades.

No definition available.

Name:	xel_PercentageOfMarginOnHybridRecsApprovedForMarginsInExcessOf20Million
Namespace Prefix:	xel_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

The recommended cost of debt by an independent third party in a rate case proceeding for 2012, filed with the applicable regulatory agency.

No definition available.

Name:	xel_RecommendationForPercentCostOfDebt
Namespace Prefix:	xel_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Rate of return on equity that an independent third party's revenue increase represented through a rate case proceeding for 2012, filed with the applicable regulatory agency.

No definition available.