Regulatory Matters - Deferred Fuel and Purchased Power Regulatory Asset (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Change in regulatory asset
Deferred fuel and purchased power	$ 78,277	$ 48,405	$ 60,303
Deferred fuel and purchased power amortization	(116,750)	14,767	(38,152)
ARIZONA PUBLIC SERVICE COMPANY
Change in regulatory asset
Deferred fuel and purchased power	78,277	48,405	60,303
Deferred fuel and purchased power amortization	(116,750)	14,767	(38,152)
ACC | ARIZONA PUBLIC SERVICE COMPANY | Power Supply Adjustor (PSA)
Change in regulatory asset
Beginning balance	75,637	12,465
Deferred fuel and purchased power	78,277	48,405
Deferred fuel and purchased power amortization	(116,750)	14,767
Ending balance	$ 37,164	$ 75,637	$ 12,465