Stock Plans: (Compensation Expense and Respective Tax Benefit (Charge) for Performance Share Unit Awards) (Details) - Performance Shares - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2026	Sep. 30, 2025	Sep. 30, 2026	Sep. 30, 2025
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Compensation Expense related to PSU Awards	$ (1)	$ 6	$ 52	$ 66
Tax Benefit/(Charge) Related to PSU Awards	$ 3	$ 1	$ 30	$ 18

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
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Amount of tax benefit for recognition of expense of award under share-based payment arrangement.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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