Share-based compensation plans - Company's SARs (Details) - Stock Appreciation Rights (SARs) - $ / shares	12 Months Ended
Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Number of Shares
Beginning Balance (in shares)	729,515
Vested (in shares)	0
Granted (in shares)	0
Exercised (in shares)	(47,180)
Forfeited/Expired (in shares)	(18,931)
Ending Balance (in shares)	663,404	729,515
Exercisable (in shares)	663,404
Average Grant Date Fair Value Per Share
Beginning Balance, weighted-average exercise price (usd per share)	$ 55.13
Vested, weighted-average exercise price (usd per share)	0
Granted, weighted-average exercise price (usd per share)	0
Exercised, weighted-average exercise price (usd per share)	47.28
Forfeited/Expired, weighted average exercise price (usd per share)	57.41
Ending Balance, weighted average exercise price (usd per share)	55.62	$ 55.13
Exercisable, weighted-average exercise price (usd per share)	$ 55.62
Nonvested
Number of Shares
Beginning Balance (in shares)	0
Vested (in shares)	0
Granted (in shares)	0	0	0
Exercised (in shares)	0
Forfeited/Expired (in shares)	0
Ending Balance (in shares)	0	0
Exercisable (in shares)	0
Vested
Number of Shares
Beginning Balance (in shares)	729,515
Vested (in shares)	0
Granted (in shares)	0
Exercised (in shares)	(47,180)
Forfeited/Expired (in shares)	(18,931)
Ending Balance (in shares)	663,404	729,515
Exercisable (in shares)	663,404

Share based compensation arrangement by share based payment award options vested in period.

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- Definition

Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Vested in Period, Weighted Average Exercise Price

+ References

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- Definition

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).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(01)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

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- Definition

The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan.

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- Definition

Number of options outstanding, including both vested and non-vested options.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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Weighted-average exercise price, at which grantee can acquire shares reserved for issuance, for fully vested and expected to vest exercisable or convertible options. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

+ References

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- Definition

Weighted average price at which option holders acquired shares when converting their stock options into shares.

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Weighted average price at which grantees could have acquired the underlying shares with respect to stock options that were terminated.

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- Definition

Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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- Definition

Number of share options (or share units) exercised during the current period.

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