Changes in Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	$ 6,159,876	$ 6,021,460
OCI (loss) before reclassifications	(616)	252
Amounts reclassified from accumulated other comprehensive loss	515	901
Ending balance	6,164,451	6,050,136
APS
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	7,052,955	6,750,473
Ending balance	7,218,379	6,929,796
Pension and Other Postretirement Benefits
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(32,332)	(53,885)
OCI (loss) before reclassifications	0	0
Amounts reclassified from accumulated other comprehensive loss	515	901
Ending balance	(31,817)	(52,984)
Pension and Other Postretirement Benefits | APS
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(15,596)	(34,880)
OCI (loss) before reclassifications	0	0
Amounts reclassified from accumulated other comprehensive loss	457	820
Ending balance	(15,139)	(34,060)
Derivative Instruments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	897	(976)
OCI (loss) before reclassifications	(616)	252
Amounts reclassified from accumulated other comprehensive loss	0	0
Ending balance	281	(724)
Accumulated Other Comprehensive Loss
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(31,435)	(54,861)
Ending balance	(31,536)	(53,708)
Accumulated Other Comprehensive Loss | APS
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(15,596)	(34,880)
Ending balance	$ (15,139)	$ (34,060)