v3.25.1
Changes in Accumulated Other Comprehensive Loss (Details) - USD ($)
$ in Thousands
 3 Months Ended
Mar. 31, 2025
Mar. 31, 2024
Changes in accumulated other comprehensive income (loss) by component    
Beginning balance $ 6,857,478 $ 6,284,862
Other comprehensive income (loss) before reclassifications 350 0
Amounts reclassified from accumulated other comprehensive loss 498 562
Ending balance 6,845,982 6,310,533
Accumulated Other Comprehensive Loss    
Changes in accumulated other comprehensive income (loss) by component    
Beginning balance (30,942) (33,144)
Ending balance (30,094) (32,582)
Pension and Other Postretirement Benefits    
Changes in accumulated other comprehensive income (loss) by component    
Beginning balance (31,661) (34,754)
Other comprehensive income (loss) before reclassifications 0 0
Amounts reclassified from accumulated other comprehensive loss 498 562
Ending balance (31,163) (34,192)
Derivative Instruments    
Changes in accumulated other comprehensive income (loss) by component    
Beginning balance 719 1,610
Other comprehensive income (loss) before reclassifications 350 0
Amounts reclassified from accumulated other comprehensive loss 0 0
Ending balance 1,069 1,610
APS    
Changes in accumulated other comprehensive income (loss) by component    
Beginning balance 8,376,332 7,349,136
Ending balance 8,381,322 7,369,047
APS | Accumulated Other Comprehensive Loss    
Changes in accumulated other comprehensive income (loss) by component    
Beginning balance (14,116) (17,219)
Ending balance (13,710) (16,729)
APS | Pension and Other Postretirement Benefits    
Changes in accumulated other comprehensive income (loss) by component    
Beginning balance (14,116) (17,219)
Other comprehensive income (loss) before reclassifications 0 0
Amounts reclassified from accumulated other comprehensive loss 406 490
Ending balance $ (13,710) $ (16,729)