Changes in Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	$ 6,164,451	$ 6,050,136	$ 6,159,876	$ 6,021,460
OCI (loss) before reclassifications	(536)	(2,206)	(1,152)	(1,954)
Amounts reclassified from accumulated other comprehensive loss	481	1,100	996	2,001
Ending balance	6,076,137	6,021,523	6,076,137	6,021,523
APS
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	7,218,379	6,929,796	7,052,955	6,750,473
Ending balance	7,134,586	6,899,284	7,134,586	6,899,284
Pension and Other Postretirement Benefits
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(31,817)	(52,984)	(32,332)	(53,885)
OCI (loss) before reclassifications	(982)	(3,213)	(982)	(3,213)
Amounts reclassified from accumulated other comprehensive loss	481	1,100	996	2,001
Ending balance	(32,318)	(55,097)	(32,318)	(55,097)
Pension and Other Postretirement Benefits | APS
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(15,139)	(34,060)	(15,596)	(34,880)
OCI (loss) before reclassifications	(839)	(3,160)	(839)	(3,160)
Amounts reclassified from accumulated other comprehensive loss	431	999	888	1,819
Ending balance	(15,547)	(36,221)	(15,547)	(36,221)
Derivative Instruments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	281	(724)	897	(976)
OCI (loss) before reclassifications	446	1,007	(170)	1,259
Amounts reclassified from accumulated other comprehensive loss	0	0	0	0
Ending balance	727	283	727	283
Accumulated Other Comprehensive Loss
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(31,536)	(53,708)	(31,435)	(54,861)
Ending balance	(31,591)	(54,814)	(31,591)	(54,814)
Accumulated Other Comprehensive Loss | APS
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(15,139)	(34,060)	(15,596)	(34,880)
Ending balance	$ (15,547)	$ (36,221)	$ (15,547)	$ (36,221)