Commitments and Contingencies - Schedule of Long-term Commitments (Parenthetical) (Detail) $ in Millions	Sep. 30, 2023 USD ($)
Other Commitments [Line Items]
Contractual obligations	$ 2,733
Fuel And Gas Supply [Member]
Other Commitments [Line Items]
Contractual obligations	387
Fuel And Gas Supply [Member] \| Tampa Electric [Member]
Other Commitments [Line Items]
Contractual obligations	$ 3

Amount of contractual obligation, including, but not limited to, long-term debt, lease obligation, purchase obligation, and other commitments.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480678/235-10-S99-3

Name:	us-gaap_ContractualObligation
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant