Earnings per share (Details) - CAD ($) $ / shares in Units, $ in Thousands	12 Months Ended
Sep. 30, 2022	Sep. 30, 2021
Earnings per share [line items]
Basic net earnings	$ 1,466,142	$ 1,369,072
Diluted net earnings	$ 1,466,142	$ 1,369,072
Basic weighted average number of ordinary shares outstanding (in shares)	239,262,004	249,119,219
Net effect of dilutive stock options and PSUs (in shares)	3,605,441	3,969,661
Diluted weighted average number of ordinary shares outstanding (in shares)	242,867,445	253,088,880
Basic earnings per share (CAD per share)	$ 6.13	$ 5.50
Diluted earnings per share (CAD per share)	$ 6.04	$ 5.41
Anti-dilutive securities excluded from computation of earnings per share (in shares)	307,272	1,276,809
Class A subordinate voting shares \| Capital stock
Earnings per share [line items]
Anti-dilutive securities excluded from computation of earnings per share (in shares)	1,841,709	15,460,465
PSUs \| Class A subordinate voting shares \| Capital stock
Earnings per share [line items]
Anti-dilutive securities excluded from computation of earnings per share (in shares)	8,839,439	1,433,521

Antidilutive Securities Excluded From Computation Of Earnings Per Share, Amount

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The weighted average number of ordinary shares outstanding plus the weighted average number of ordinary shares that would be issued on the conversion of all the dilutive potential ordinary shares into ordinary shares. [Refer: Ordinary shares [member]; Weighted average [member]]

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The amount of profit (loss) attributable to ordinary equity holders of the parent entity (the numerator) divided by the weighted average number of ordinary shares outstanding during the period (the denominator).

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The amount of profit (loss) attributable to ordinary equity holders of the parent entity (the numerator), divided by the weighted average number of ordinary shares outstanding during the period (the denominator), both adjusted for the effects of all dilutive potential ordinary shares. [Refer: Ordinary shares [member]; Weighted average [member]]

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The profit (loss) attributable to ordinary equity holders of the parent entity. [Refer: Profit (loss)]

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The number of ordinary shares outstanding at the beginning of the period, adjusted by the number of ordinary shares bought back or issued during the period multiplied by a time-weighting factor.

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