Business Segments (Detail) - CAD ($) $ in Millions		3 Months Ended
		Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Revenues and other income
Revenues	[1]	$ 12,249	$ 12,057
Investment and other income (note 3)		34	64
Total revenues and other income		12,283	12,121
Expenses
Exploration		1	1
Purchases of crude oil and products	[2]	7,706	7,478
Production and manufacturing	[3]	1,664	1,756
Selling and general	[3]	246	186
Federal excise tax and fuel charge		591	529
Depreciation and depletion		490	490
Non-service pension and postretirement benefit		1	20
Financing (note 5)	[4]	12	16
Total expenses		10,711	10,476
Income (loss) before income taxes		1,572	1,645
Income taxes		377	397
Net income (loss)		1,195	1,248
Cash flows from (used in) operating activities		1,076	(821)
Capital and exploration expenditures		496	429
Total assets as at March 31		42,513	42,115	$ 41,199
Corporate and other
Revenues and other income
Revenues		0	0
Investment and other income (note 3)		17	42
Total revenues and other income		17	42
Expenses
Exploration		0	0
Purchases of crude oil and products		0	0
Production and manufacturing		2	0
Selling and general		60	4
Federal excise tax and fuel charge		0	0
Depreciation and depletion		9	7
Non-service pension and postretirement benefit		1	20
Financing (note 5)		11	16
Total expenses		83	47
Income (loss) before income taxes		(66)	(5)
Income taxes		(15)	0
Net income (loss)		(51)	(5)
Cash flows from (used in) operating activities		181	28
Capital and exploration expenditures		48	30
Total assets as at March 31		2,699	3,815
Eliminations
Revenues and other income
Revenues		(5,960)	(5,536)
Total revenues and other income		(5,960)	(5,536)
Expenses
Exploration		0	0
Purchases of crude oil and products		(5,958)	(5,535)
Production and manufacturing		0	0
Selling and general		(2)	(1)
Federal excise tax and fuel charge		0	0
Depreciation and depletion		0	0
Non-service pension and postretirement benefit		0	0
Financing (note 5)		0	0
Total expenses		(5,960)	(5,536)
Income (loss) before income taxes		0	0
Income taxes		0	0
Net income (loss)		0	0
Cash flows from (used in) operating activities		0	0
Capital and exploration expenditures		0	0
Total assets as at March 31		(490)	(771)
Upstream | Intersegment Eliminations
Revenues and other income
Revenues		4,122	3,622
Upstream | Operating Segments
Revenues and other income
Revenues		42	76
Investment and other income (note 3)		4	2
Total revenues and other income		4,168	3,700
Expenses
Exploration		1	1
Purchases of crude oil and products		1,813	1,543
Production and manufacturing		1,188	1,287
Selling and general		0	0
Federal excise tax and fuel charge		0	0
Depreciation and depletion		432	434
Non-service pension and postretirement benefit		0	0
Financing (note 5)		1	0
Total expenses		3,435	3,265
Income (loss) before income taxes		733	435
Income taxes		175	105
Net income (loss)		558	330
Cash flows from (used in) operating activities		891	(398)
Capital and exploration expenditures		290	321
Total assets as at March 31		28,661	29,059
Downstream | Intersegment Eliminations
Revenues and other income
Revenues		1,748	1,823
Downstream | Operating Segments
Revenues and other income
Revenues		11,879	11,639
Investment and other income (note 3)		12	20
Total revenues and other income		13,639	13,482
Expenses
Exploration		0	0
Purchases of crude oil and products		11,591	11,196
Production and manufacturing		421	411
Selling and general		162	157
Federal excise tax and fuel charge		590	528
Depreciation and depletion		45	45
Non-service pension and postretirement benefit		0	0
Financing (note 5)		0	0
Total expenses		12,809	12,337
Income (loss) before income taxes		830	1,145
Income taxes		199	275
Net income (loss)		631	870
Cash flows from (used in) operating activities		7	(419)
Capital and exploration expenditures		153	74
Total assets as at March 31		11,126	9,535
Chemical | Intersegment Eliminations
Revenues and other income
Revenues		90	91
Chemical | Operating Segments
Revenues and other income
Revenues		328	342
Investment and other income (note 3)		1	0
Total revenues and other income		419	433
Expenses
Exploration		0	0
Purchases of crude oil and products		260	274
Production and manufacturing		53	58
Selling and general		26	26
Federal excise tax and fuel charge		1	1
Depreciation and depletion		4	4
Non-service pension and postretirement benefit		0	0
Financing (note 5)		0	0
Total expenses		344	363
Income (loss) before income taxes		75	70
Income taxes		18	17
Net income (loss)		57	53
Cash flows from (used in) operating activities		(3)	(32)
Capital and exploration expenditures		5	4
Total assets as at March 31		$ 517	$ 477

[1] (a) Amounts from related parties included in revenues.2,729 3,136 

[2] (b) Amounts to related parties included in purchases of crude oil and products.985 1,078 

[3] (c) Amounts to related parties included in production and manufacturing, and selling and general expenses.150 135 

[4] (d) Amounts to related parties included in financing.44 39