Regulatory - Additional Information (Detail)											1 Months Ended		6 Months Ended
	Aug. 06, 2021 USD ($)	Aug. 03, 2021 USD ($)	Nov. 19, 2020 USD ($)	Aug. 18, 2020 USD ($)	Aug. 03, 2020 USD ($)	Apr. 27, 2020 USD ($)	Jun. 28, 2019 USD ($) MW	Jun. 29, 2018 USD ($) MW	Dec. 12, 2017 USD ($) MW	Sep. 27, 2017 USD ($) MW	Jan. 31, 2024 USD ($)	Jan. 31, 2023 USD ($)	Jun. 30, 2021 USD ($) Unit	Dec. 31, 2020 USD ($)	Jun. 09, 2020 USD ($)
Public Utilities General Disclosures [Line Items]
Utility plant, at original costs													$ 14,346,000,000	$ 13,818,000,000
Accumulated depreciation													$ 3,897,000,000	3,712,000,000
Number of units applied for recovery | Unit													3
Intangible Software Assets [Member]
Public Utilities General Disclosures [Line Items]
Accumulated amortization reserve surplus															$ 16,000,000
Electric Utility Plant [Member]
Public Utilities General Disclosures [Line Items]
Utility plant, at original costs													$ 11,876,000,000	11,486,000,000
Peoples Gas System [Member]
Public Utilities General Disclosures [Line Items]
Increase in revenue			$ 34,000,000
Allowed equity in the capital structure			54.70%
Impact of tax reform through reduction in base revenue days			120 days
Accumulated depreciation			$ 34,000,000
Increase in annual base rate			58,000,000
Peoples Gas System [Member] | Cast Iron and Bare Steel Replacement Rider [Member]
Public Utilities General Disclosures [Line Items]
Increase in revenue			$ 24,000,000
Subsequent Event [Member]
Public Utilities General Disclosures [Line Items]
Additional cost recovery from settlement agreement		$ 83,000,000
Settlement Agreement [Member] | Subsequent Event [Member]
Public Utilities General Disclosures [Line Items]
Settlement agreement, approval date	Aug. 06, 2021
Base rate adjustment amount	$ 123,000,000
Increase in revenue	$ 191,000,000
Settlement agreement number of subsequent years adjustments	2 years
Allowed equity in the capital structure	54.00%
Basis point increase applicable	0.25%
Additional attainable revenue under settlement agreement	$ 10,000,000
Changes in base rate under agreement	$ 0
Impact of tax reform through reduction in base revenue days	180 days
Settlement Agreement [Member] | Scenario Forecast [Member]
Public Utilities General Disclosures [Line Items]
Settlement agreement adjustment amount											$ 21,000,000	$ 90,000,000
Settlement Agreement [Member] | US Treasury Bond [Member] | Subsequent Event [Member]
Public Utilities General Disclosures [Line Items]
Calculating period	30 years
Determining period	6 months
Minimum [Member] | Peoples Gas System [Member]
Public Utilities General Disclosures [Line Items]
Percentage of ROE			8.90%
Base rate agreement frozen period			Jan. 01, 2021
Minimum [Member] | Settlement Agreement [Member] | Subsequent Event [Member]
Public Utilities General Disclosures [Line Items]
Percentage of ROE	9.00%
Base rate agreement frozen period	Jan. 01, 2022
Minimum [Member] | Settlement Agreement [Member] | US Treasury Bond [Member] | Subsequent Event [Member]
Public Utilities General Disclosures [Line Items]
ROE revenue basis point on yield rate	0.50%
Maximum [Member] | Peoples Gas System [Member]
Public Utilities General Disclosures [Line Items]
Percentage of ROE			11.00%
Base rate agreement frozen period			Dec. 31, 2023
Maximum [Member] | Settlement Agreement [Member] | Subsequent Event [Member]
Public Utilities General Disclosures [Line Items]
Percentage of ROE	11.00%
Base rate agreement frozen period	Dec. 31, 2024
Mid Point [Member] | Peoples Gas System [Member]
Public Utilities General Disclosures [Line Items]
Percentage of ROE			9.90%
Mid Point [Member] | Settlement Agreement [Member] | Subsequent Event [Member]
Public Utilities General Disclosures [Line Items]
Percentage of ROE	9.95%
Solar Project Cost Recovery [Member]
Public Utilities General Disclosures [Line Items]
Settlement agreement, extended terms										four years through December 31, 2021
Settlement agreement, approval date										Nov. 06, 2017
Solar energy capacity | MW										600
Solar generation capacity investments										$ 850,000,000
Solar Project Cost Recovery [Member] | Solar Base Rate Adjustments [Member]
Public Utilities General Disclosures [Line Items]
True-up amount returned to customers				$ 5,000,000
Estimated true-up amount returned to customers													4,000,000
Solar Project Cost Recovery [Member] | Effective September 1, 2018 [Member]
Public Utilities General Disclosures [Line Items]
Solar energy capacity | MW									145
Estimated annual revenue requirements									$ 24,000,000
Solar Project Cost Recovery [Member] | Effective January 1, 2019 [Member]
Public Utilities General Disclosures [Line Items]
Solar energy capacity | MW								260
Estimated annual revenue requirements								$ 46,000,000
Solar Project Cost Recovery [Member] | Effective January 1, 2020 [Member]
Public Utilities General Disclosures [Line Items]
Solar energy capacity | MW							149
Estimated annual revenue requirements							$ 26,000,000
Solar Project Cost Recovery [Member] | Effective January 1, 2021 [Member]
Public Utilities General Disclosures [Line Items]
Solar energy capacity | MW									46
Estimated annual revenue requirements									$ 8,000,000
Solar Project Cost Recovery [Member] | Minimum [Member]
Public Utilities General Disclosures [Line Items]
Solar project investment term										2017
Solar Project Cost Recovery [Member] | Maximum [Member]
Public Utilities General Disclosures [Line Items]
Solar project investment term										2021
Retiring Assets [Member] | Settlement Agreement [Member] | Subsequent Event [Member]
Public Utilities General Disclosures [Line Items]
Cost recovery from settlement agreement	$ 68,000,000
Retiring Coal Generation Units and Meter Assets [Member] | Settlement Agreement [Member] | Subsequent Event [Member]
Public Utilities General Disclosures [Line Items]
Settlement agreement cost recovery period	15 years
Big Bend Modernization Project [Member]
Public Utilities General Disclosures [Line Items]
Energy generation capacity investments													850,000,000
Investments in energy projects till date													611,000,000
Accumulated depreciation													$ 91,000,000	88,000,000
Settlement agreement recovery description													Tampa Electric’s Settlement Agreement provides recovery for the Big Bend Modernization project in two phases. The first phase is a revenue increase to cover the costs of the assets in service during 2022, among other items. The remainder of the project costs will be recovered as part of the 2023 subsequent year adjustment.
Big Bend Modernization Project [Member] | Electric Utility Plant [Member]
Public Utilities General Disclosures [Line Items]
Utility plant, at original costs													$ 200,000,000	$ 200,000,000
Big Bend Modernization Project [Member] | Minimum [Member]
Public Utilities General Disclosures [Line Items]
Energy project investment term													2018
Big Bend Modernization Project [Member] | Maximum [Member]
Public Utilities General Disclosures [Line Items]
Energy project investment term													2023
Big Bend Coal Generation Assets [Member]
Public Utilities General Disclosures [Line Items]
Settlement agreement cost recovery period													15 years
Storm Protection Plan [Member]
Public Utilities General Disclosures [Line Items]
Cost recovery from settlement agreement					$ 39,000,000
Reduction in annual base rates						$ 15,000,000