Regulatory Matters - Deferred Fuel and Purchased Power Regulatory Asset (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Change in regulatory asset
Deferred fuel and purchased power costs — current period	$ 93,651	$ 82,481	$ 78,277
Amounts refunded/(charged) to customers	12,047	(49,508)	(116,750)
ARIZONA PUBLIC SERVICE COMPANY
Change in regulatory asset
Deferred fuel and purchased power costs — current period	93,651	82,481	78,277
Amounts refunded/(charged) to customers	12,047	(49,508)	(116,750)
ACC | ARIZONA PUBLIC SERVICE COMPANY | Power Supply Adjustor (PSA)
Change in regulatory asset
Beginning balance	70,137	37,164
Deferred fuel and purchased power costs — current period	93,651	82,481
Amounts refunded/(charged) to customers	12,047	(49,508)
Ending balance	$ 175,835	$ 70,137	$ 37,164