Employee compensation plans - Schedule of Stock Compensation Assumptions Used (Details) - Stock Appreciation Rights (SARs)	12 Months Ended
	Dec. 31, 2023 $ / shares
January 11, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term	12 days
Expected volatility factor (as a percent)	17.096%
Risk-free interest rate (as a percent)	1.741%
Quarterly dividends (in dollars per share)	$ 0.6
January 10, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term	1 year
Expected volatility factor (as a percent)	33.244%
Risk-free interest rate (as a percent)	4.75%
Quarterly dividends (in dollars per share)	$ 0.6
January 11, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term	2 years
Expected volatility factor (as a percent)	34.355%
Risk-free interest rate (as a percent)	4.244%
Quarterly dividends (in dollars per share)	$ 0.6
January 7, 2022
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term	3 years
Expected volatility factor (as a percent)	33.422%
Risk-free interest rate (as a percent)	4.008%
Quarterly dividends (in dollars per share)	$ 0.6
January 6, 2023
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term	4 years
Expected volatility factor (as a percent)	40.315%
Risk-free interest rate (as a percent)	3.927%
Quarterly dividends (in dollars per share)	$ 0.6