Employee compensation plans - Schedule of Stock Compensation Assumptions Used (Details) - Stock Appreciation Rights (SARs)	12 Months Ended
Dec. 31, 2025
January 11, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term	10 days
Expected volatility factor (as a percent)	18.737%
Risk-free interest rate (as a percent)	3.644%
January 7, 2022
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term	1 year
Expected volatility factor (as a percent)	32.074%
Risk-free interest rate (as a percent)	3.511%
January 6, 2023
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term	2 years
Expected volatility factor (as a percent)	26.223%
Risk-free interest rate (as a percent)	3.482%
January 5, 2024
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term	3 years
Expected volatility factor (as a percent)	26.10%
Risk-free interest rate (as a percent)	3.544%
January 6, 2025
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term	4 years
Expected volatility factor (as a percent)	30.414%
Risk-free interest rate (as a percent)	3.655%

The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

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- Definition

The risk-free interest rate assumption that is used in valuing an option on its own shares.

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- Definition

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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- Definition

Expected term of award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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