Retirement Benefits (Narrative) (Details) - USD ($) $ in Millions	6 Months Ended
Jun. 30, 2026	Jun. 30, 2025
Defined Benefit Plan Disclosure [Line Items]
Deferred credits refund period (in years)	10 years
DB Pension Plans \| Volatility Mechanism
Defined Benefit Plan Disclosure [Line Items]
Deferred credits (costs)	$ 4	$ 1
OPEB Plan \| Volatility Mechanism
Defined Benefit Plan Disclosure [Line Items]
Deferred credits (costs)	$ 6	$ 5

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