Stock Plans: (Compensation Expense and Respective Tax Benefit (Charge) for Restricted Share Unit Awards) (Details) - Restricted Stock Units (RSUs) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Compensation Expense Related to RSU Awards	$ 41	$ 34	$ 113	$ 97
Tax Benefit/(Charge) Related to RSU Awards	$ 11	$ 6	$ 43	$ 26

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
-Name Accounting Standards Codification
-Section S45
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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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