Revenue - Summary of Disaggregates TEC Revenue by Major Source (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Disaggregation Of Revenue [Line Items]
Total electric revenue	$ 649	$ 548
Total revenue	649	548
Residential [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	336	304
Commercial [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	172	155
Industrial [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	46	40
Regulatory Deferrals [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	10	(23)
Unbilled Revenue [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	4	3
Other [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	$ 81	$ 69