Employee compensation plans - Schedule of Stock Appreciation Rights (Details) - Stock Appreciation Rights (SARs)	12 Months Ended
	Dec. 31, 2021 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of OARs Outstanding (in shares) | shares	2,458,646
Total weighted average strike price (in dollars per share)	$ 27.11
Total weighted average remaining contractual life	3 years 1 month 6 days
Total weighted average fair value (in dollars per share)	$ 21.12
January 6, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of OARs Outstanding (in shares) | shares	367,320
Strike price (in dollars per share)	$ 18.90
Remaining contractual life	5 days
Fair value (in dollars per share)	$ 27.47
January 5, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of OARs Outstanding (in shares) | shares	436,010
Strike price (in dollars per share)	$ 27.05
Remaining contractual life	1 year
Fair value (in dollars per share)	$ 19.22
January 11, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of OARs Outstanding (in shares) | shares	509,216
Strike price (in dollars per share)	$ 26.45
Remaining contractual life	2 years
Fair value (in dollars per share)	$ 21.49
January 10, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of OARs Outstanding (in shares) | shares	522,720
Strike price (in dollars per share)	$ 27.54
Remaining contractual life	3 years
Fair value (in dollars per share)	$ 20.90
January 11, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of OARs Outstanding (in shares) | shares	623,380
Strike price (in dollars per share)	$ 32.16
Remaining contractual life	4 years
Fair value (in dollars per share)	$ 18.59