Revenue Recognition - Schedule of Sales to Members and Sales to Non-Members (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Revenue Recognition
Total operating revenues	$ 633,748	$ 564,090	$ 1,311,324	$ 1,100,404
Sales to members
Revenue Recognition
Total operating revenues	601,690	562,267	1,269,991	1,097,637
Sales to members \| Capacity revenues
Revenue Recognition
Total operating revenues	422,959	401,710	836,296	757,428
Sales to members \| Energy revenues
Revenue Recognition
Total operating revenues	178,731	160,557	433,695	340,209
Sales to non-members
Revenue Recognition
Total operating revenues	32,058	1,823	41,333	2,767
Sales to non-members \| Capacity revenues
Revenue Recognition
Total operating revenues	0	786	0	1,572
Sales to non-members \| Energy revenues
Revenue Recognition
Total operating revenues	$ 32,058	$ 1,037	$ 41,333	$ 1,195

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, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

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+ Details