Related Party Transactions - Schedule of NRG's Material Related Party Transactions (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Related Party Transaction [Line Items]
Revenue	$ 7,481	$ 6,740	$ 17,737	$ 15,325
Related Party
Related Party Transaction [Line Items]
Revenue	14	12	36	25
Related Party \| Gladstone
Related Party Transaction [Line Items]
Revenue	0	0	1	1
Related Party \| Ivanpah
Related Party Transaction [Line Items]
Revenue	$ 14	$ 12	$ 35	$ 24

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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+ Details

- Definition

Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

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+ Details