Retirement Plans and Other Benefits Retirement Plans and Other Benefits - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Plan Design Changes [Abstract]
Amount of other postretirement benefit trust assets for union employee medical costs	$ 186,000,000
Partnership funding commitments, contribution amount (up to)	75,000,000
Partnership funding commitments, funded amount	$ 62,000,000
Pension Benefits
Plan Design Changes [Abstract]
Expected long-term return on plan assets for next fiscal year (as a percent)	6.25%
Contributions
Employer contributions	$ 50,000,000	$ 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)	$ 350,000,000
Other Benefits
Plan Design Changes [Abstract]
Expected long-term return on plan assets for next fiscal year (as a percent)	5.55%
Contributions
Employer contributions	$ 0	353,000
Employee savings plan benefits
Retiree medical cost reimbursement	72,000,000
Pinnacle West
Employee savings plan benefits
Expenses recorded for the defined contribution savings plan	$ 11,000,000	10,000,000	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	$ 0	$ 1,000,000	$ 1,000,000