Retirement Plans and Other Postretirement Benefits - Additional Information (Details) - USD ($)		12 Months Ended
	Jan. 04, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Initial pre-65 ultimate health care cost trend rate (as a percent)		4.75%	4.75%
Initial post-65 healthcare cost trend rate (as a percent)		2.00%	4.75%
Funded percentage (more than)		100.00%
Partnership funding commitments, contribution amount (up to)		$ 50,000,000
Partnership funding commitments, funded amount		38,000,000
Minimum contributions under MAP-21
Voluntary employer contributions over next three years (up to)		$ 100,000,000
Subsequent Event
Defined Benefit Plan Disclosure [Line Items]
Transfer to active union medical account	$ (106,000,000)
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Expected long-term return on plan assets for next fiscal year (as a percent)		5.30%
Contributions
Employer contributions		$ 100,000,000	$ 150,000,000	$ 50,000,000
Minimum contributions under MAP-21
Minimum contributions under MAP-21		$ 0
Pension Benefits | Subsequent Event
Defined Benefit Plan Disclosure [Line Items]
Transfer to active union medical account	(106,000,000)
Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Expected long-term return on plan assets for next fiscal year (as a percent)		5.05%
Contributions
Employer contributions		$ 0	0
Minimum contributions under MAP-21
Retiree medical cost reimbursement		26,000,000	30,000,000	72,000,000
Other Benefits | Subsequent Event
Defined Benefit Plan Disclosure [Line Items]
Transfer to active union medical account	$ 106,000,000
Pinnacle West
Minimum contributions under MAP-21
Expenses recorded for the defined contribution savings plan		$ 11,000,000	$ 11,000,000	$ 11,000,000
ARIZONA PUBLIC SERVICE COMPANY
Minimum contributions under MAP-21
APS's employees share of total cost of the plans (as a percent)		99.00%