Income taxes - Components of Deferred Income Tax Liabilities and Assets (Detail) - CAD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Depreciation and amortization	$ 5,388	$ 5,284	$ 5,319
Successful drilling and land acquisitions	236	331	363
Pension and benefits	(105)	(303)	(534)
Asset retirement obligation	(529)	(418)	(403)
Capitalized interest	127	120	120
LIFO inventory valuation	(454)	(413)	(150)
Tax loss carryforwards	(84)	(42)	(460)
Valuation allowance	73	0	0
Other	(53)	(101)	(154)
Net deferred income tax liabilities	$ 4,599	$ 4,458	$ 4,101

Deferred Tax Assets Inventory Noncurrent

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Deferred Tax Assets Other Non Current

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The tax effect as of the balance sheet date of the amount of the estimated future tax effects arising from successful drilling and land acquisitions expensed for tax purposes, but capitalized for conformity with gaap.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible capital loss carryforwards.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from pension benefits.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from asset retirement obligations. An asset retirement obligation is a legal obligation associated with the disposal or retirement from service of a tangible long-lived asset.

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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Amount, after deferred tax asset, of deferred tax liability attributable to taxable differences without jurisdictional netting.

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Amount of deferred tax liability attributable to taxable temporary differences from capitalized interest.

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Amount of deferred tax liability attributable to taxable temporary differences from property, plant, and equipment.

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