Changes in Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Changes in accumulated other comprehensive income (loss) by component
Beginning balance	$ 5,553,188	$ 5,348,705
Ending balance	5,752,793	5,553,188
Pension and Other Postretirement Benefits
Changes in accumulated other comprehensive income (loss) by component
Beginning balance	(56,522)	(45,997)
OCI (loss) before reclassifications	(8,370)	(14,041)
Amounts reclassified from accumulated other comprehensive loss	4,167	3,516
Ending balance	(60,725)	(56,522)
Derivative Instruments
Changes in accumulated other comprehensive income (loss) by component
Beginning balance	(574)	(1,711)
OCI (loss) before reclassifications	(2,089)	0
Amounts reclassified from accumulated other comprehensive loss	592	1,137
Ending balance	(2,071)	(574)
Accumulated Other Comprehensive Income (Loss)
Changes in accumulated other comprehensive income (loss) by component
Beginning balance	(57,096)	(47,708)
OCI (loss) before reclassifications	(10,459)	(14,041)
Amounts reclassified from accumulated other comprehensive loss	4,759	4,653
Ending balance	(62,796)	(57,096)
ARIZONA PUBLIC SERVICE COMPANY
Changes in accumulated other comprehensive income (loss) by component
Beginning balance	5,998,803	5,786,797
Ending balance	6,345,185	5,998,803
ARIZONA PUBLIC SERVICE COMPANY | Pension and Other Postretirement Benefits
Changes in accumulated other comprehensive income (loss) by component
Beginning balance	(34,948)	(25,396)
OCI (loss) before reclassifications	(9,568)	(12,572)
Amounts reclassified from accumulated other comprehensive loss	3,598	3,020
Ending balance	(40,918)	(34,948)
ARIZONA PUBLIC SERVICE COMPANY | Derivative Instruments
Changes in accumulated other comprehensive income (loss) by component
Beginning balance	(574)	(1,711)
OCI (loss) before reclassifications	(18)	0
Amounts reclassified from accumulated other comprehensive loss	592	1,137
Ending balance	0	(574)
ARIZONA PUBLIC SERVICE COMPANY | Accumulated Other Comprehensive Income (Loss)
Changes in accumulated other comprehensive income (loss) by component
Beginning balance	(35,522)	(27,107)
OCI (loss) before reclassifications	(9,586)	(12,572)
Amounts reclassified from accumulated other comprehensive loss	4,190	4,157
Ending balance	$ (40,918)	$ (35,522)