Business segments (Detail) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Revenues and other income
Revenues	$ 59,413	$ 37,508	$ 22,284
Investment and other income (note 8, 18)	257	82	104
Total revenues and other income	59,670	37,590	22,388
Expenses
Exploration (note 15)	5	32	13
Purchases of crude oil and products (note 11)	37,742	23,174	13,293
Production and manufacturing (note 11)	7,404	6,316	5,535
Selling and general	882	784	741
Federal excise tax and fuel charge	2,179	1,928	1,736
Depreciation and depletion (note 11)	1,897	1,977	3,293
Non-service pension and postretirement benefit	17	42	121
Financing (note 12)	60	54	64
Total expenses	50,186	34,307	24,796
Income (loss) before income taxes (note 11)	9,484	3,283	(2,408)
Income taxes (note 3)	2,144	804	(551)
Net income (loss) (note 11)	7,340	2,479	(1,857)
Cash flows from (used in) operating activities	10,482	5,476	798
Capital and exploration expenditures	1,490	1,140	874
Property, plant and equipment
Cost	54,568	56,762	55,771
Accumulated depreciation and depletion	(24,062)	(25,522)	(23,737)
Net property, plant and equipment	30,506	31,240	32,034
Total assets	43,524	40,782	38,031
Corporate and other
Revenues and other income
Revenues	0	0	0
Investment and other income (note 8, 18)	79	10	19
Total revenues and other income	79	10	19
Expenses
Exploration (note 15)	0	0	0
Purchases of crude oil and products (note 11)	0	0	0
Production and manufacturing (note 11)	0	0	0
Selling and general	150	128	35
Federal excise tax and fuel charge	0	0	0
Depreciation and depletion (note 11)	27	26	24
Non-service pension and postretirement benefit	17	42	121
Financing (note 12)	54	39	61
Total expenses	248	235	241
Income (loss) before income taxes (note 11)	(169)	(225)	(222)
Income taxes (note 3)	(38)	(53)	(52)
Net income (loss) (note 11)	(131)	(172)	(170)
Cash flows from (used in) operating activities	(59)	(47)	(64)
Capital and exploration expenditures	57	24	41
Property, plant and equipment
Cost	863	806	782
Accumulated depreciation and depletion	(343)	(316)	(290)
Net property, plant and equipment	520	490	492
Total assets	5,312	3,196	1,632
Eliminations
Revenues and other income
Revenues	(27,134)	(14,795)	(4,172)
Total revenues and other income	(27,134)	(14,795)	(4,172)
Expenses
Exploration (note 15)	0	0	0
Purchases of crude oil and products (note 11)	(27,128)	(14,789)	(4,167)
Production and manufacturing (note 11)	0	0	0
Selling and general	(6)	(6)	(5)
Federal excise tax and fuel charge	0	0	0
Depreciation and depletion (note 11)	0	0	0
Non-service pension and postretirement benefit	0	0	0
Financing (note 12)	0	0	0
Total expenses	(27,134)	(14,795)	(4,172)
Income (loss) before income taxes (note 11)	0	0	0
Income taxes (note 3)	0	0	0
Net income (loss) (note 11)	0	0	0
Cash flows from (used in) operating activities	16	10	(8)
Capital and exploration expenditures	0	0	0
Property, plant and equipment
Cost	0	0	0
Accumulated depreciation and depletion	0	0	0
Net property, plant and equipment	0	0	0
Total assets	(386)	(249)	(398)
Upstream
Revenues and other income
Revenues	494	5,863	6,263
Investment and other income (note 8, 18)	135	12	7
Expenses
Exploration (note 15)	5	32	13
Purchases of crude oil and products (note 11)	7,971	7,492	4,834
Production and manufacturing (note 11)	5,491	4,661	3,852
Selling and general	0	0	0
Federal excise tax and fuel charge	0	0	0
Depreciation and depletion (note 11)	1,673	1,775	3,084
Non-service pension and postretirement benefit	0	0	0
Financing (note 12)	5	15	3
Total expenses	15,145	13,975	11,786
Income (loss) before income taxes (note 11)	4,619	1,856	(2,989)
Income taxes (note 3)	974	461	(671)
Net income (loss) (note 11)	3,645	1,395	(2,318)
Cash flows from (used in) operating activities	5,834	4,913	286
Capital and exploration expenditures	1,128	632	561
Property, plant and equipment
Cost	45,784	48,200	47,693
Accumulated depreciation and depletion	(18,835)	(20,389)	(18,786)
Net property, plant and equipment	26,949	27,811	28,907
Total assets	28,830	29,416	31,835
Upstream | Intersegment Eliminations
Revenues and other income
Revenues	19,135	9,956	2,527
Upstream | Operating Segments
Revenues and other income
Total revenues and other income	19,764	15,831	8,797
Downstream
Revenues and other income
Revenues	57,466	30,207	15,178
Investment and other income (note 8, 18)	43	59	78
Expenses
Exploration (note 15)	0	0	0
Purchases of crude oil and products (note 11)	55,569	29,505	12,047
Production and manufacturing (note 11)	1,640	1,445	1,468
Selling and general	653	572	619
Federal excise tax and fuel charge	2,177	1,928	1,736
Depreciation and depletion (note 11)	179	158	166
Non-service pension and postretirement benefit	0	0	0
Financing (note 12)	1	0	0
Total expenses	60,219	33,608	16,036
Income (loss) before income taxes (note 11)	4,766	1,178	700
Income taxes (note 3)	1,144	283	147
Net income (loss) (note 11)	3,622	895	553
Cash flows from (used in) operating activities	4,415	179	470
Capital and exploration expenditures	295	476	251
Property, plant and equipment
Cost	6,926	6,772	6,321
Accumulated depreciation and depletion	(4,143)	(4,096)	(3,962)
Net property, plant and equipment	2,783	2,676	2,359
Total assets	9,277	7,945	4,554
Downstream | Intersegment Eliminations
Revenues and other income
Revenues	7,476	4,520	1,480
Downstream | Operating Segments
Revenues and other income
Total revenues and other income	64,985	34,786	16,736
Chemical
Revenues and other income
Revenues	1,453	1,438	843
Investment and other income (note 8, 18)	0	1	0
Expenses
Exploration (note 15)	0	0	0
Purchases of crude oil and products (note 11)	1,330	966	579
Production and manufacturing (note 11)	273	210	215
Selling and general	85	90	92
Federal excise tax and fuel charge	2	0	0
Depreciation and depletion (note 11)	18	18	19
Non-service pension and postretirement benefit	0	0	0
Financing (note 12)	0	0	0
Total expenses	1,708	1,284	905
Income (loss) before income taxes (note 11)	268	474	103
Income taxes (note 3)	64	113	25
Net income (loss) (note 11)	204	361	78
Cash flows from (used in) operating activities	276	421	114
Capital and exploration expenditures	10	8	21
Property, plant and equipment
Cost	995	984	975
Accumulated depreciation and depletion	(741)	(721)	(699)
Net property, plant and equipment	254	263	276
Total assets	491	474	408
Chemical | Intersegment Eliminations
Revenues and other income
Revenues	523	319	165
Chemical | Operating Segments
Revenues and other income
Total revenues and other income	$ 1,976	$ 1,758	$ 1,008