Income Taxes: (Schedule of Income Taxes Paid by Jurisdiction) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
United States:
U.S. Federal	$ 797
U.S. State and Local	107
Total United States	904
Foreign:
Total Foreign	2,948
Total	3,852	$ 3,178	$ 2,952
Switzerland
Foreign:
Total Foreign	929
Russia:
Foreign:
Total Foreign	348
Italy
Foreign:
Total Foreign	301
Other Foreign Jurisdictions
Foreign:
Total Foreign	$ 1,370