Revenue - Schedule of Disaggregation (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Disaggregation of Revenue [Line Items]
Total operating revenues	$ 1,121,703	$ 1,061,669	$ 2,066,658	$ 1,845,200
Regulatory cost recovery revenue	10,000	(2,000)	33,000	10,000
Retail Electric Service | Residential
Disaggregation of Revenue [Line Items]
Total operating revenues	542,315	537,589	952,039	904,935
Retail Electric Service | Non-Residential
Disaggregation of Revenue [Line Items]
Total operating revenues	516,712	462,669	922,849	822,185
Wholesale Energy Sales
Disaggregation of Revenue [Line Items]
Total operating revenues	27,282	29,902	122,885	58,805
Transmission Services for Others
Disaggregation of Revenue [Line Items]
Total operating revenues	33,152	29,352	64,943	54,844
Other Sources
Disaggregation of Revenue [Line Items]
Total operating revenues	2,242	2,157	3,942	4,431
Electric and Transmission Service
Disaggregation of Revenue [Line Items]
Total operating revenues	$ 1,112,000	$ 1,064,000	$ 2,034,000	$ 1,835,000