Income Taxes: (Schedule of Reasons Attributable to the Differences Between Effective Income Tax Rate and Federal Statutory Rate) (Details)	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Increase (decrease) resulting from:
U.S. federal statutory rate	21.00%	21.00%	21.00%
Foreign rate differences		(1.60%)	(1.00%)
Dividend repatriation cost		0.60%	0.70%
Global intangible low-taxed income		1.70%	2.00%
U.S. state taxes		0.60%	(0.10%)
Foreign derived intangible income		(0.70%)	(0.90%)
Foreign exchange		1.70%	(1.60%)
Non-deductible goodwill impairment		0.00%	1.30%
Fair value adjustment of equity securities		1.10%	0.10%
Other		(0.30%)	(0.80%)
Effective tax rate	19.70%	24.70%	22.40%
Russia
Increase (decrease) resulting from:
Unremitted earnings of Russian subsidiaries		0.006	0.017