Revenue - Summary of Disaggregates TEC Revenue by Major Source (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Disaggregation Of Revenue [Line Items]
Total electric revenue	$ 724	$ 795	$ 1,944	$ 2,024
Total revenue	724	795	1,944	2,024
Residential [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	471	567	1,160	1,322
Commercial [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	190	234	522	605
Industrial [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	42	56	124	152
Regulatory Deferrals [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	(56)	(137)	(106)	(297)
Unbilled Revenue [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	1	(8)	28	16
Other [Member]
Disaggregation Of Revenue [Line Items]
Total electric revenue	$ 76	$ 83	$ 216	$ 226