Share-based compensation plans - Company's SARs (Details)	12 Months Ended
Dec. 31, 2021 $ / shares shares
Stock Appreciation Rights (SARs)
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Beginning Balance (in shares)	1,271,428
Vested (in shares)	0
Granted (in shares)	0
Exercised (in shares)	(363,102)
Forfeited/Expired (in shares)	(28,655)
Ending Balance (in shares)	879,671
Exercisable (in shares)	755,507
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Beginning Balance, weighted-average exercise price (usd per share) \| $ / shares	$ 53.83
Granted, weighted-average exercise price (usd per share) \| $ / shares	0
Exercised, weighted-average exercise price (usd per share) \| $ / shares	50.95
Forfeited/Expired, weighted average exercise price (usd per share) \| $ / shares	53.12
Ending Balance, weighted average exercise price (usd per share) \| $ / shares	55.03
Exercisable, weighted-average exercise price (usd per share) \| $ / shares	$ 54.08
Stock Appreciation Rights (SARs) \| Nonvested
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Beginning Balance (in shares)	397,677
Vested (in shares)	259,687
Granted (in shares)	0
Exercised (in shares)	0
Forfeited/Expired (in shares)	(13,826)
Ending Balance (in shares)	124,164
Exercisable (in shares)	0
Stock Appreciation Rights (SARs) \| Vested
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Beginning Balance (in shares)	873,751
Vested (in shares)	259,687
Granted (in shares)	0
Exercised (in shares)	(363,102)
Forfeited/Expired (in shares)	(14,829)
Ending Balance (in shares)	755,507
Exercisable (in shares)	755,507
Restricted Stock Awards
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Granted (in shares)	201,570
Restricted Stock Awards \| Nonvested
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Granted (in shares)	201,570
Restricted Stock Awards \| Vested
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Granted (in shares)	0

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

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

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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 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.

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

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

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