Risk Management, Derivative Instruments and Hedging Activities - Schedule of Statements of Operations Presentation (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Unrealized gain (loss) on commodity contracts	$ (211)	$ 92	$ (365)	$ (90)
Realized and unrealized gain (loss) on interest rate contracts	(147)	218	(586)	(50)
Interest rate derivatives
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Realized and unrealized gain (loss) on interest rate contracts	9	0	11	(13)
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Derivative Instruments and Hedging Activities Disclosures [Line Items]
Realized gain (loss) on commodity contracts	65	43	(262)	16
Unrealized gain (loss) on commodity contracts	(212)	176	(324)	(65)
Location, Statement of Income, Balance [Axis]: tln:EnergyExpenses
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Unrealized gain (loss) on commodity contracts	1	(84)	(41)	(25)
Location, Statement of Income, Balance [Axis]: tln:OperatingExpenseFuelUsedAndPurchasedPower
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Realized gain (loss) on commodity contracts	$ (26)	$ (5)	$ 26	$ 19

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Amount of realized and unrealized gain (loss) of derivative instruments not designated or qualifying as hedging instruments.

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The difference between the book value and the sale price of agreements to purchase or sell mineral resources, energy, and agricultural products at some future point. This element refers to the gain (loss) included in earnings and not to the cash proceeds.

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The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of open agreements to purchase or sell mineral resources, energy, and agricultural products at some future point held at each balance sheet date, that was included in earnings for the period.

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