Retirement Plans and Other Benefits Retirement Plans and Other Benefits - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Partnership funding commitments, contribution amount (up to)	$ 50,000,000
Partnership funding commitments, funded amount	$ 38,000,000
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Funded percentage (more than)	100.00%
Expected long-term return on plan assets for next fiscal year (as a percent)	5.75%
Contributions
Employer contributions	$ 150,000,000	$ 50,000,000	$ 100,000,000
Minimum contributions under MAP-21
Minimum contributions under MAP-21	0
Voluntary employer contributions over next three years (up to)	$ 100,000,000
Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Expected long-term return on plan assets for next fiscal year (as a percent)	5.00%
Contributions
Employer contributions	$ 0	0
Minimum contributions under MAP-21
Retiree medical cost reimbursement	30,000,000	72,000,000
Pinnacle West
Employee savings plan benefits
Expenses recorded for the defined contribution savings plan	$ 11,000,000	$ 11,000,000	10,000,000
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 | Other Benefits
Contributions
Employer contributions			$ 1,000,000