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Commitments and Contingencies - Superfund-Related Matters and Southwest Power Outage (Details) (Arizona Public Service Company, USD $)
In Millions, unless otherwise specified
 0 Months Ended 3 Months Ended 0 Months Ended
Sep. 08, 2011
Customer
kV
Mar. 31, 2015
Aug. 06, 2013
Defendant
Superfund-Related Matters      
Costs related to investigation and study under Superfund site   $ 2pnw_CostsRelatedToInvestigationAndStudyUnderSuperfundSite  
Southwest Power Outage      
Capacity of transmission line that tripped out of service (in kV) 500pnw_PowerOutageCapacityofTransmissionLinethatTrippedoutofService    
Period, after the transmission line went off-line, over which generation and transmission resources for the Yuma area were lost 10 minutes    
Number of customers losing service in Yuma area 69,700pnw_PowerOutageNumberOfCustomersLosingService    
Contaminated groundwater wells
      
Superfund-Related Matters      
Number of defendants against whom Roosevelt Irrigation District (RID) filed lawsuit     24us-gaap_LossContingencyNumberOfDefendants
/ dei_LegalEntityAxis
= pnw_ArizonaPublicServiceCompanyMember
/ us-gaap_LossContingenciesByNatureOfContingencyAxis
= pnw_ContaminatedGroundwaterWellsMember