Revenue Recognition - Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2025	Mar. 31, 2024
Disaggregation of revenue
Revenue from contracts with customers	$ 864	$ 925
Operating lease income	27	25
Total operating revenues	891	950
Transferred over time
Disaggregation of revenue
Revenue from contracts with customers	714	729
Transferred over time \| Retail service
Disaggregation of revenue
Revenue from contracts with customers	660	678
Transferred over time \| Other service
Disaggregation of revenue
Revenue from contracts with customers	54	51
Transferred at point in time \| Equipment sales
Disaggregation of revenue
Revenue from contracts with customers	$ 150	$ 196

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.

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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- 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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