Financing costs (Detail) - CAD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Financing costs and additional notes and loans payable information [Abstract]
Debt-related interest		$ 48	$ 53	$ 152	$ 148
Capitalized interest		(39)	(37)	(119)	(100)
Net interest expense		9	16	33	48
Other interest		2	3	4	3
Total financing	[1]	$ 11	$ 19	$ 37	$ 51

[1] (d) Amounts to related parties included in financing.40 44 127 124