Leases - Additional Information (Detail) - Tampa Electric [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Operating Leased Assets [Line Items]
Operating lease, description	Tampa Electric has operating leases for buildings, land, telecommunication services and rail cars.
Operating lease, existence of option to extend	true
Operating lease options to extend	options to extend the leases for up to an additional 65 years.
Operating lease expense	$ 5	$ 4	$ 4
Maximum [Member]
Operating Leased Assets [Line Items]
Operating lease renewal term	61 years
Minimum [Member]
Operating Leased Assets [Line Items]
Operating lease renewal term	1 year