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Retirement Plans and Other Benefits Retirement Plans and Other Benefits (Details)
 1 Months Ended 12 Months Ended
Jul. 31, 2012
Dec. 31, 2017
USD ($)
Dec. 31, 2016
USD ($)
Dec. 31, 2015
USD ($)
Dec. 31, 2014
USD ($)
Dec. 31, 2013
USD ($)
Dec. 31, 2012
USD ($)
Dec. 31, 2011
USD ($)
Jan. 01, 2015
Age
Plan Design Changes [Abstract]                  
Amount of other postretirement benefit trust assets for union employee medical costs   $ 186,000,000              
Amount of pension and other postretirement benefit costs deferred             $ 14,000,000 $ 11,000,000  
Regulatory asset amortization period 3 years                
Amortization of regulatory assets       $ 5,000,000 $ 8,000,000 $ 8,000,000 $ 4,000,000    
Partnership funding commitments, contribution amount (up to)   75,000,000              
Partnership funding commitments, funded amount   $ 58,000,000              
Pension Benefits                  
Plan Design Changes [Abstract]                  
Expected long-term return on plan assets for next fiscal year (as a percent)   6.05%              
Contributions                  
Employer's contributions under the plan   $ 100,000,000 $ 100,000,000 100,000,000          
Minimum contributions under MAP-21                  
Minimum contributions under MAP-21   0              
Voluntary employer contributions over next three years (up to)   $ 250,000,000              
Other Benefits                  
Plan Design Changes [Abstract]                  
Age eligible for benefit | Age                 65
Effect of plan amendment on accumulated benefit obligation       316,000,000          
Expected long-term return on plan assets for next fiscal year (as a percent)   5.55%              
Contributions                  
Employer's contributions under the plan   $ 353,000 819,000 1,000,000          
Pinnacle West                  
Employee savings plan benefits                  
Expenses recorded for the defined contribution savings plan   $ 10,000,000 10,000,000 9,000,000          
ARIZONA PUBLIC SERVICE COMPANY                  
Employee savings plan benefits                  
APS's employees share of total cost of the plans (as a percent)   99.00%              
ARIZONA PUBLIC SERVICE COMPANY | Pension Benefits                  
Contributions                  
Employer's contributions under the plan   $ 100,000,000 100,000,000 100,000,000          
ARIZONA PUBLIC SERVICE COMPANY | Other Benefits                  
Contributions                  
Employer's contributions under the plan   $ 1,000,000 $ 1,000,000 $ 1,000,000