Employee Postretirement Benefits - Additional Information (Detail) - USD ($)			12 Months Ended
		Jan. 02, 2017	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Redemption frequency description			The redemption frequency of the funds ranges from daily to weekly and the redemption notice period ranges from 1 business day to 30 business days.
Percentage of qualified pension plan's actuarial value of assets			100.38%	110.22%
Employer contributions			$ 10,000,000	$ 10,000,000	$ 15,000,000
Employer matching contribution percentage of eligible participant contribution		75.00%				70.00%
Description of defined contribution plan			Effective January 1, 2017, the employer matching contributions increased from 70% to 75% with an additional incentive match of up to 25% of eligible participant contributions based on the achievement of certain operating company financial goals.
Defined contribution plan cost recognized			$ 20,000,000	18,000,000	22,000,000
Defined benefit plan additional percentage of eligible compensation for matching contributions by employer			25.00%
Non-qualified SERP [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan, assets			$ 4,000,000	4,000,000
Unfunded [Member]
Defined Benefit Plan Disclosure [Line Items]
Commitments			0
Tampa Electric [Member]
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit cost			0	1,000,000	4,000,000
Employer contributions			10,000,000	10,000,000	12,000,000
Employer contributions in next fiscal year			11,000,000
Defined contribution plan cost recognized			20,000,000	18,000,000	19,000,000
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit cost			0	1,000,000	8,000,000
Defined benefit plan, assets			14,000,000	10,000,000
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit cost			4,000,000	5,000,000	9,000,000
Defined benefit plan, assets			0	0
Other Postretirement Benefits [Member] | Tampa Electric [Member]
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit cost			4,000,000	5,000,000	8,000,000
Employer contributions in next fiscal year			10,000,000
SERP [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions			0	0	0
Benefits paid			0	5,000,000	2,000,000
Non Elective Employer Contribution [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined contribution plan cost recognized			11,000,000	10,000,000	10,000,000
TECO Energy [Member]
Defined Benefit Plan Disclosure [Line Items]
Accumulated benefit obligation of defined benefit pension plans			$ 638,000,000	642,000,000
Percentage of defined benefit plan's actual return			5.10%
Defined contribution plan, employer match percentage			6.00%
Employer matching contribution percentage of eligible participant contribution			75.00%
TECO Energy [Member] | Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit cost			$ 4,000,000	3,000,000	9,000,000
Settlement charge	[1]		0	(2,000,000)	(2,000,000)
Commitments			674,000,000	678,000,000	666,000,000
Employer contributions			16,000,000	16,000,000
TECO Energy [Member] | Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit cost	[2]		5,000,000	6,000,000	8,000,000
Settlement charge	[1],[2]		0	0	0
Commitments	[3]		130,000,000	132,000,000	$ 142,000,000
Employer contributions	[3]		0	$ 0
TECO Energy [Member] | Other Postretirement Benefits Florida-Based Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Other postretirement benefit plans service benefit to be amortized from regulatory assets in next fiscal year			$ 0

[1] Represents TECO Energy’s SERP and Restoration settlement charges as a result of the retirement of certain executives. These charges did impact TEC’s financial statements.

[2] Represents amounts for TECO Energy’s Florida-based other postretirement benefit plan

[3] Represent amounts for TECO Energy’s Florida-based other postretirement benefit plan.