Share-based payments (Details) - USD ($) $ / shares in Units, $ in Millions	9 Months Ended
Sep. 30, 2023	Sep. 30, 2022
Time-based shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	3 years
Performance-based shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	3 years
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expiration period	10 years
Stock options \| First anniversary
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting percentage	20.00%
Stock options \| Second anniversary
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting percentage	30.00%
Stock options \| Third anniversary
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting percentage	50.00%
Restricted stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate fair value at grant date	$ 12.1	$ 11.7
Granted (in shares)	296,000	183,000
Average grant price (in usd per share)	$ 41.03	$ 63.68

Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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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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Percentage of vesting of award under share-based payment arrangement.

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Intrinsic value of nonvested award under share-based payment arrangement. Excludes share and unit options.

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No definition available.

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- Definition

Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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