Leases - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Operating Leased Assets [Line Items]
Operating lease, description	TEC 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
Option to purchase assets related to CNG stations	Customers have the option to purchase the assets related to the CNG stations at any time after year five of the agreements, which was in 2021, by paying a make-whole payment at the date of the purchase based on a targeted internal rate of return.
Maximum [Member]
Operating Leased Assets [Line Items]
Operating lease renewal term	64 years
Minimum [Member]
Operating Leased Assets [Line Items]
Operating lease renewal term	1 year