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Retirement Plans and Other Benefits - Fair Value of Pinnacle West's Pension Plan (Details) - USD ($)
$ in Thousands
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Pension Benefits      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Fair value of plan assets $ 2,542,774 $ 2,615,404 $ 2,264,121
Pension Benefits | Pinnacle West      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Net receivables (payables) 14,467 16,883  
Fair value of plan assets 2,542,774 2,615,404  
Pension Benefits | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pinnacle West      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 640,679 556,660  
Pension Benefits | Significant Other Observable Inputs (Level 2) | Pinnacle West      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 1,845,531 2,013,932  
Pension Benefits | Significant Unobservable Inputs (Level 3) | Pinnacle West      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 42,097 27,929  
Other Benefits      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Fair value of plan assets 833,017 834,625 748,339
Other Benefits | Pinnacle West      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Net receivables (payables) 3,096 4,100  
Fair value of plan assets 833,017 834,625  
Other Benefits | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pinnacle West      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 454,891 414,204  
Other Benefits | Significant Other Observable Inputs (Level 2) | Pinnacle West      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 375,030 416,321  
Other Benefits | Significant Unobservable Inputs (Level 3) | Pinnacle West      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 0 0  
Cash and cash equivalents | Pension Benefits | Pinnacle West      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Fair value of plan assets 1,893 387  
Cash and cash equivalents | Pension Benefits | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pinnacle West      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 1,893 387  
Cash and cash equivalents | Other Benefits | Pinnacle West      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Fair value of plan assets 240 318  
Cash and cash equivalents | Other Benefits | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pinnacle West      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 240 318  
Corporate | Pension Benefits | Pinnacle West      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Fair value of plan assets 1,108,736 1,162,096  
Corporate | Pension Benefits | Significant Other Observable Inputs (Level 2) | Pinnacle West      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 1,108,736 1,162,096  
Corporate | Other Benefits | Pinnacle West      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Fair value of plan assets 217,026 187,961  
Corporate | Other Benefits | Significant Other Observable Inputs (Level 2) | Pinnacle West      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 217,026 187,961  
U.S. Treasury | Pension Benefits | Pinnacle West      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Fair value of plan assets 274,778 291,817  
U.S. Treasury | Pension Benefits | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pinnacle West      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 274,778 291,817  
U.S. Treasury | Other Benefits | Pinnacle West      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Fair value of plan assets 131,435 130,967  
U.S. Treasury | Other Benefits | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pinnacle West      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 131,435 130,967  
Other (a) | Pension Benefits | Pinnacle West      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Fair value of plan assets 113,008 113,265  
Other (a) | Pension Benefits | Significant Other Observable Inputs (Level 2) | Pinnacle West      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 113,008 113,265  
Other (a) | Other Benefits | Pinnacle West      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Fair value of plan assets 31,106 35,291  
Other (a) | Other Benefits | Significant Other Observable Inputs (Level 2) | Pinnacle West      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 31,106 35,291  
U.S. companies | Pension Benefits | Pinnacle West      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Fair value of plan assets 233,021 246,387  
U.S. companies | Pension Benefits | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pinnacle West      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 233,021 246,387  
U.S. companies | Other Benefits | Pinnacle West      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Fair value of plan assets 253,193 265,106  
U.S. companies | Other Benefits | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pinnacle West      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 253,193 265,106  
International companies | Pension Benefits | Pinnacle West      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Fair value of plan assets 14,680 18,069  
International companies | Pension Benefits | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pinnacle West      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 14,680 18,069  
International companies | Other Benefits | Pinnacle West      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Fair value of plan assets 12,390 17,813  
International companies | Other Benefits | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pinnacle West      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 12,390 17,813  
U.S. equities | Pension Benefits | Pinnacle West      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Fair value of plan assets 130,097 127,336  
U.S. equities | Pension Benefits | Significant Other Observable Inputs (Level 2) | Pinnacle West      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 130,097 127,336  
U.S. equities | Other Benefits | Pinnacle West      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Fair value of plan assets 81,516 88,258  
U.S. equities | Other Benefits | Significant Other Observable Inputs (Level 2) | Pinnacle West      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 81,516 88,258  
International equities | Pension Benefits | Pinnacle West      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Fair value of plan assets 185,892 317,167  
International equities | Pension Benefits | Significant Other Observable Inputs (Level 2) | Pinnacle West      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 185,892 317,167  
International equities | Other Benefits | Pinnacle West      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Fair value of plan assets 28,539 85,746  
International equities | Other Benefits | Significant Other Observable Inputs (Level 2) | Pinnacle West      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 28,539 85,746  
Real estate | Pension Benefits | Pinnacle West      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Fair value of plan assets 150,359 129,715  
Real estate | Pension Benefits | Significant Other Observable Inputs (Level 2) | Pinnacle West      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 150,359 129,715  
Real estate | Other Benefits | Pinnacle West      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Fair value of plan assets 13,512 11,657  
Real estate | Other Benefits | Significant Other Observable Inputs (Level 2) | Pinnacle West      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 13,512 11,657  
Partnerships | Pension Benefits | Pinnacle West      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Fair value of plan assets 169,937 166,266  
Partnerships | Pension Benefits | Significant Other Observable Inputs (Level 2) | Pinnacle West      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 127,840 138,337  
Partnerships | Pension Benefits | Significant Unobservable Inputs (Level 3) | Pinnacle West      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 42,097 27,929  
Mutual funds - International equities | Pension Benefits | Pinnacle West      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Fair value of plan assets 116,307    
Mutual funds - International equities | Pension Benefits | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pinnacle West      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 116,307    
Mutual funds - International equities | Other Benefits | Pinnacle West      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Fair value of plan assets 52,568    
Mutual funds - International equities | Other Benefits | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pinnacle West      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 52,568    
Short-term investments and other | Pension Benefits | Pinnacle West      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Net receivables (payables) 14,467 16,883  
Fair value of plan assets 44,066 42,899  
Short-term investments and other | Pension Benefits | Significant Other Observable Inputs (Level 2) | Pinnacle West      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 29,599 26,016  
Short-term investments and other | Pension Benefits | Significant Unobservable Inputs (Level 3)      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Fair value of plan assets 42,097 27,929 $ 8,660
Short-term investments and other | Other Benefits | Pinnacle West      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Net receivables (payables) 3,096 4,100  
Fair value of plan assets 11,492 11,508  
Short-term investments and other | Other Benefits | Quoted Prices in Active Markets for Identical Assets (Level 1) | Pinnacle West      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets 5,065    
Short-term investments and other | Other Benefits | Significant Other Observable Inputs (Level 2) | Pinnacle West      
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category      
Gross fair value of plan assets $ 3,331 $ 7,408