Asset Retirement Obligations - Additional information (Details) - APS $ in Millions	9 Months Ended
	Sep. 30, 2025 USD ($)
Cholla
Schedule of Asset Retirement Obligations [Line Items]
Increase (decrease) in asset retirement obligation	$ 48
Four Corners Coal-Fired Power Plant
Schedule of Asset Retirement Obligations [Line Items]
Increase (decrease) in asset retirement obligation	(5)
Navajo Coal-Fired Power Plant
Schedule of Asset Retirement Obligations [Line Items]
Increase (decrease) in asset retirement obligation	$ (4)