Changes in Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	$ 6,021,523	$ 5,834,899	$ 6,021,460	$ 5,752,793
OCI (loss) before reclassifications	513	(194)	(1,441)	(187)
Amounts reclassified from accumulated other comprehensive loss	1,001	1,106	3,002	3,317
Ending balance	6,362,113	6,186,464	6,362,113	6,186,464
APS
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	6,899,284	6,412,290	6,750,473	6,345,185
Ending balance	7,236,194	6,761,259	7,236,194	6,761,259
Pension and Other Postretirement Benefits
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(55,097)	(59,639)	(53,885)	(60,725)
OCI (loss) before reclassifications	0	0	(3,213)	(1,125)
Amounts reclassified from accumulated other comprehensive loss	1,001	1,106	3,002	3,317
Ending balance	(54,096)	(58,533)	(54,096)	(58,533)
Pension and Other Postretirement Benefits | APS
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(36,221)	(39,832)	(34,880)	(40,918)
OCI (loss) before reclassifications	0	0	(3,160)	(914)
Amounts reclassified from accumulated other comprehensive loss	909	1,000	2,728	3,000
Ending balance	(35,312)	(38,832)	(35,312)	(38,832)
Derivative Instruments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	283	(939)	(976)	(2,071)
OCI (loss) before reclassifications	513	(194)	1,772	938
Amounts reclassified from accumulated other comprehensive loss	0	0	0	0
Ending balance	796	(1,133)	796	(1,133)
Accumulated Other Comprehensive Loss
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(54,814)	(60,578)	(54,861)	(62,796)
Ending balance	(53,300)	(59,666)	(53,300)	(59,666)
Accumulated Other Comprehensive Loss | APS
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(36,221)	(39,832)	(34,880)	(40,918)
Ending balance	$ (35,312)	$ (38,832)	$ (35,312)	$ (38,832)