Stock-based compensation - Weighted-Average Fair Value Assumptions (Details) - Stock Options	3 Months Ended
	Mar. 31, 2024 $ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected option life (years)	4 years 9 months
Risk-free interest rate	3.88%
Expected share price volatility	28.38%
Expected annual dividends per share (in cad per share)	$ 0.760
Expected forfeiture rate	3.12%
Weighted-average grant date fair value per option granted during the period (in cad per share)	$ 33.27