Retirement Benefit Plans - Assumed Healthcare Trend Rates (Details) - Postretirement Medical Benefits	12 Months Ended
Dec. 31, 2025	Dec. 31, 2024
Defined Benefit Plan, Plan Assets, Category [Line Items]
Ultimate trend rate	4.00%	4.00%
Year that trend reaches ultimate rate	2050	2047
Health care cost trend rate assumed next year
Defined Benefit Plan, Plan Assets, Category [Line Items]
Healthcare cost trend rate assumption	7.65%	8.40%

Assumed rate, for next fiscal year, based on annual change in cost of health care cost benefits used to measure expected cost of benefits covered by defined benefit postretirement plan. Factors include, but are not limited to, estimate of health care inflation, change in health care utilization or delivery pattern, technological advances, and change in health status of participant. Excludes factors for change in composition of plan population by age and dependency status.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Ultimate trend rate for health care cost for defined benefit postretirement plan.

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Year ultimate health care cost trend rate is expected to be reached, in YYYY format.

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