Revenue - Schedule of Disaggregation (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Disaggregation of Revenue [Line Items]
Total operating revenues	$ 1,637,759	$ 1,469,871	$ 3,704,417	$ 3,315,071
Regulatory cost recovery revenue	3,000	5,000	36,000	16,000
Retail Electric Service | Residential
Disaggregation of Revenue [Line Items]
Total operating revenues	883,393	743,061	1,835,432	1,647,996
Retail Electric Service | Non-Residential
Disaggregation of Revenue [Line Items]
Total operating revenues	649,164	547,979	1,572,013	1,370,164
Wholesale Energy Sales
Disaggregation of Revenue [Line Items]
Total operating revenues	57,801	139,741	180,686	198,546
Transmission Services for Others
Disaggregation of Revenue [Line Items]
Total operating revenues	43,286	36,321	108,229	91,165
Other Sources
Disaggregation of Revenue [Line Items]
Total operating revenues	4,115	2,769	8,057	7,200
Electric and Transmission Service
Disaggregation of Revenue [Line Items]
Total operating revenues	$ 1,635,000	$ 1,465,000	$ 3,668,000	$ 3,299,000