Retirement Plans and Other Benefits - Fair Value of Pinnacle West's Pension Plan (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Pension Benefits
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Fair value of plan assets	$ 2,615,404	$ 2,264,121	$ 2,079,181
Pension Benefits | Pinnacle West
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Net receivables (payables)	16,883	250
Fair value of plan assets	2,615,404	2,264,121
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	556,660	490,559
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	2,013,932	1,764,652
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	27,929	8,660
Other Benefits
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Fair value of plan assets	834,625	748,339	684,221
Other Benefits | Pinnacle West
Fair value of Pinnacle West's pension plan and other postretirement benefit plan assets, by asset category
Net receivables (payables)	4,100	2,430
Fair value of plan assets	834,625	748,339
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	414,204	371,777
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	416,321	374,132
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 equivalent funds | 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	387	504
Cash and cash equivalent funds | 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	387	504
Cash and cash equivalent funds | 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	318
Cash and cash equivalent funds | 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	318
Corporate debt | 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	1,162,096	898,621
Corporate debt | 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	1,162,096	898,621
Corporate debt | 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	187,961	153,888
Corporate debt | 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	187,961	153,888
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	291,817	231,590
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	291,817	231,590
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	130,967	98,704
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	130,967	98,704
Other | 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	113,265	84,011
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	113,265	84,011
Other | 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	35,291	27,936
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	35,291	27,936
U.S. companies, 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	246,387	239,036
U.S. companies, 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	246,387	239,036
U.S. companies, 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	265,106	252,181
U.S. companies, 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	265,106	252,181
International companies, 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	18,069	19,429
International companies, 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	18,069	19,429
International companies, 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	17,813	20,892
International companies, 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	17,813	20,892
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	127,336	116,150
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	127,336	116,150
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	88,258	80,751
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	88,258	80,751
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	317,167	367,551
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	317,167	367,551
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	85,746	92,382
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	85,746	92,382
Fixed income securities | 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		137,520
Fixed income securities | 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		137,520
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	129,715	119,739
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	129,715	119,739
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	11,657	10,761
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	11,657	10,761
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	166,266	8,660
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	138,337	0
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	27,929	8,660
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)	16,883	250
Fair value of plan assets	42,899	41,310
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	26,016	41,060
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	27,929	8,660	2,419
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)	4,100	2,430
Fair value of plan assets	11,508	10,844
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	$ 7,408	$ 8,414