Income Taxes: (Schedule of Reasons Attributable to the Differences Between Effective Income Tax Rate and Federal Statutory Rate, Current Year) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Effective Income Tax Rate Reconciliation [Line Items]
Earnings before income taxes	$ 13,880	$ 12,199	$ 10,450
Amount
Provision Computed at Statutory U.S. Tax Rate	2,915
Effect of Cross-Border Tax Laws	67
Nontaxable/Nondeductible Items	(17)
Valuation Allowances	519
Foreign Exchange	(384)
Deferred Taxes on Canadian Equity Investment	(343)
Total provision for income taxes	$ 2,737	$ 3,017	$ 2,339
Percentage
Provision Computed at Statutory U.S. Tax Rate	21.00%	21.00%	21.00%
State and Local Income Taxes		0.60%	(0.10%)
Swiss Federal Rate Differential		(1.60%)	(1.00%)
Other		(0.30%)	(0.80%)
Effect of Cross-Border Tax Laws	0.50%
Nontaxable/Nondeductible Items	(0.10%)
Valuation Allowances	3.80%
Foreign Exchange	(2.80%)
Deferred Taxes on Canadian Equity Investment	(2.50%)
Effective tax rate	19.70%	24.70%	22.40%
United States
Amount
State and Local Income Taxes	$ (12)
Other	$ (232)
Percentage
State and Local Income Taxes	(0.10%)
Other	(1.70%)
Switzerland:
Amount
Federal Rate Differential	$ (920)
Other	$ (10)
Percentage
Swiss Federal Rate Differential	(6.60%)
Other	(0.10%)
Vaud, Switzerland
Amount
State and Local Income Taxes	$ 248
Percentage
State and Local Income Taxes	1.80%
Neuchatel, Switzerland
Amount
State and Local Income Taxes	$ 255
Percentage
State and Local Income Taxes	1.80%
Russia:
Amount
Federal Rate Differential	$ 263
Percentage
Swiss Federal Rate Differential	1.90%
Other Foreign Jurisdictions
Amount
Federal Rate Differential	$ 388
Percentage
Swiss Federal Rate Differential	2.80%