Revenue - Schedule of Disaggregation (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Disaggregation of Revenue [Line Items]
Total operating revenues	$ 1,061,669	$ 1,000,249	$ 1,845,200	$ 1,696,724
Regulatory cost recovery revenue	(2,000)	20,000	10,000	34,000
Retail Electric Service | Residential
Disaggregation of Revenue [Line Items]
Total operating revenues	537,589	531,717	904,935	872,555
Retail Electric Service | Non-Residential
Disaggregation of Revenue [Line Items]
Total operating revenues	462,669	420,995	822,185	735,778
Wholesale Energy Sales
Disaggregation of Revenue [Line Items]
Total operating revenues	29,902	18,007	58,805	35,604
Transmission Services for Others
Disaggregation of Revenue [Line Items]
Total operating revenues	29,352	22,579	54,844	41,572
Other Sources
Disaggregation of Revenue [Line Items]
Total operating revenues	2,157	6,951	4,431	11,215
Electric and Transmission Service
Disaggregation of Revenue [Line Items]
Total operating revenues	$ 1,064,000	$ 980,000	$ 1,835,000	$ 1,663,000