Cenovus Energy (CVE) 40-F 9 Feb 21 2020 FY Annual report (Canada) Financial data

Document and Entity Information

Document and Entity Information	12 Months Ended
	Dec. 31, 2020shares
Document And Entity Information [Abstract]
Document Type	40-F
Amendment Flag	false
Document Period End Date	Dec. 31, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Trading Symbol	CVE
Entity Registrant Name	CENOVUS ENERGY INC.
Entity Central Index Key	0001475260
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Common Stock, Shares Outstanding	1,228,869,903
Entity Emerging Growth Company	false
Entity Address, State or Province	AB
Entity Address, Country	CA

Consolidated Statements of Earn

Consolidated Statements of Earnings (Loss) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenues
Gross Sales	$ 13,591	$ 21,353	$ 21,389
Less: Royalties	364	1,173	546
Revenue	13,227	20,180	20,843
Expenses
Purchased Product	5,119	8,378	8,684
Transportation and Blending	4,444	5,184	5,942
Operating	1,930	2,088	2,184
Inventory Write-Down (Reversal)	555	49	60
(Gain) Loss on Risk Management	308	156	305
Depreciation, Depletion and Amortization	3,464	2,249	2,131
Exploration Expense	91	82	2,123
General and Administrative	292	331	1,020
Finance Costs	536	511	627
Interest Income	(9)	(12)	(19)
Transaction Costs	29
Foreign Exchange (Gain) Loss, Net	(181)	(404)	854
Re-measurement of Contingent Payment	(80)	164	50
(Gain) Loss on Divestiture of Assets	(81)	(2)	795
Other (Income) Loss, Net	40	9	13
Earnings (Loss) From Continuing Operations Before Income Tax	(3,230)	1,397	(3,926)
Income Tax Expense (Recovery)	(851)	(797)	(1,010)
Net Earnings (Loss) From Continuing Operations	(2,379)	2,194	(2,916)
Net Earnings (Loss) From Discontinued Operations			247
Net Earnings (Loss)	$ (2,379)	$ 2,194	$ (2,669)
Basic and Diluted Earnings (Loss) Per Share ($)
Continuing Operations	$ (1.94)	$ 1.78	$ (2.37)
Discontinued Operations			0.20
Net Earnings (Loss) Per Share	$ (1.94)	$ 1.78	$ (2.17)

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Loss) - CAD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement Of Comprehensive Income [Abstract]
Net Earnings (Loss)		$ (2,379)	$ 2,194	$ (2,669)
Items That Will Not be Reclassified to Profit or Loss:
Actuarial Gain (Loss) Relating to Pension and Other Post-Retirement Benefits		(8)	5	(3)
Change in the Fair Value of Equity Instruments at FVOCI	[1]		12	1
Items That May be Reclassified to Profit or Loss:
Foreign Currency Translation Adjustment		(44)	(228)	397
Total Other Comprehensive Income (Loss), Net of Tax		(52)	(211)	395
Comprehensive Income (Loss)		$ (2,431)	$ 1,983	$ (2,274)
[1]	Fair value through other comprehensive income (loss) (“FVOCI”).

Consolidated Balance Sheets

Consolidated Balance Sheets - CAD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Current Assets
Cash and Cash Equivalents	$ 378	$ 186
Accounts Receivable and Accrued Revenues	1,488	1,556
Income Tax Receivable	21	10
Inventories	1,089	1,532
Total Current Assets	2,976	3,284
Exploration and Evaluation Assets	623	787
Property, Plant and Equipment, Net	25,411	27,834
Right-of-Use Assets, Net	1,139	1,325
Other Assets	313	211
Deferred Income Taxes	36
Goodwill	2,272	2,272
Total Assets	32,770	35,713
Current Liabilities
Accounts Payable and Accrued Liabilities	2,018	2,229
Short-Term Borrowings	121
Lease Liabilities	184	196
Contingent Payment	36	79
Income Tax Payable		17
Total Current Liabilities	2,359	2,521
Long-Term Debt	7,441	6,699
Lease Liabilities	1,573	1,720
Contingent Payment	27	64
Decommissioning Liabilities	1,248	1,235
Other Liabilities	181	241
Deferred Income Taxes	3,234	4,032
Total Liabilities	16,063	16,512
Shareholders’ Equity	16,707	19,201
Total Liabilities and Shareholders’ Equity	$ 32,770	$ 35,713

Consolidated Statements of Shar

Consolidated Statements of Shareholders' Equity - CAD ($) $ in Millions	Total	Share Capital [Member]	Paid in Surplus [Member]	Retained Earnings [Member]	AOCI [Member]	[1]
Beginning balance at Dec. 31, 2017	$ 19,981	$ 11,040	$ 4,361	$ 3,937	$ 643
Net Earnings (Loss)	(2,669)			(2,669)
Other Comprehensive Income (Loss)	395				395
Comprehensive Income (Loss)	(2,274)			(2,669)	395
Stock-Based Compensation Expense	6		6
Dividends on Common Shares	(245)			(245)
Ending balance at Dec. 31, 2018	17,468	11,040	4,367	1,023	1,038
Net Earnings (Loss)	2,194			2,194
Other Comprehensive Income (Loss)	(211)				(211)
Comprehensive Income (Loss)	1,983			2,194	(211)
Stock-Based Compensation Expense	10		10
Dividends on Common Shares	(260)			(260)
Ending balance at Dec. 31, 2019	19,201	11,040	4,377	2,957	827
Net Earnings (Loss)	(2,379)			(2,379)
Other Comprehensive Income (Loss)	(52)				(52)
Comprehensive Income (Loss)	(2,431)			(2,379)	(52)
Stock-Based Compensation Expense	14		14
Dividends on Common Shares	(77)			(77)
Ending balance at Dec. 31, 2020	$ 16,707	$ 11,040	$ 4,391	$ 501	$ 775
[1]	Accumulated other comprehensive income (loss) (“AOCI”).

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Operating Activities
Net Earnings (Loss)	$ (2,379)	$ 2,194	$ (2,669)
Depreciation, Depletion and Amortization	3,464	2,249	2,131
Exploration Expense	91	82	2,123
Inventory Write-Down (Reversal)	555	49	60
Deferred Income Tax Expense (Recovery)	(838)	(814)	(794)
Unrealized (Gain) Loss on Risk Management	56	149	(1,249)
Unrealized Foreign Exchange (Gain) Loss	(131)	(827)	649
Re-measurement of Contingent Payment	(80)	164	50
(Gain) Loss on Discontinuance			(301)
(Gain) Loss on Divestiture of Assets	(81)	(2)	795
Unwinding of Discount on Decommissioning Liabilities	57	58	63
Realized Inventory Write-Down	(572)	(71)	(13)
Realized Foreign Exchange (Gain) Loss on Non-Operating Items	(33)	401	206
Other	38	70	670
Net Change in Other Assets and Liabilities	(72)	(84)	(72)
Net Change in Non-Cash Working Capital	198	(333)	505
Cash From (Used in) Operating Activities	273	3,285	2,154
Investing Activities
Capital Expenditures – Exploration and Evaluation Assets	(48)	(73)	(55)
Capital Expenditures – Property, Plant and Equipment	(811)	(1,110)	(1,322)
Proceeds From Divestitures	38	1	1,050
Net Change in Investments and Other	(4)	(133)	9
Net Change in Non-Cash Working Capital	(38)	(117)	(295)
Cash From (Used in) Investing Activities	(863)	(1,432)	(613)
Net Cash Provided (Used) Before Financing Activities	(590)	1,853	1,541
Financing Activities
Issuance (Repayment) of Short-Term Borrowings	117
Issuance of Long-Term Debt	1,326
Repayment of Long-Term Debt	(112)	(2,279)	(1,144)
Net Issuance (Repayment) of Revolving Long-Term Debt	(220)	276	(20)
Principal Repayment of Leases	(197)	(150)
Dividends Paid on Common Shares	(77)	(260)	(245)
Other			(1)
Cash From (Used in) Financing Activities	837	(2,413)	(1,410)
Foreign Exchange Gain (Loss) on Cash and Cash Equivalents Held in Foreign Currency	(55)	(35)	40
Increase (Decrease) in Cash and Cash Equivalents	192	(595)	171
Cash and Cash Equivalents, Beginning of Year	186	781	610
Cash and Cash Equivalents, End of Year	$ 378	$ 186	$ 781

Description of Business and Seg

Description of Business and Segmented Disclosures	12 Months Ended
	Dec. 31, 2020
Disclosure Of Reportable Segments [Abstract]
Description of Business and Segmented Disclosures	1. DESCRIPTION OF BUSINESS AND SEGMENTED DISCLOSURES Cenovus Energy Inc. and its subsidiaries, (together “Cenovus” or the “Company”) are in the business of developing, producing and marketing crude oil, natural gas liquids (“NGLs”) and natural gas in Canada with marketing activities and refining operations in the United States (“U.S.”). Cenovus is incorporated under the “ Canada Business Corporations Act On October 25, 2020, Cenovus announced that it had entered into a definitive agreement to combine with Husky Energy Inc. (“Husky”). The transaction was accomplished through a plan of arrangement (the “Arrangement”) pursuant to which Cenovus acquired all the issued and outstanding common shares of Husky in exchange for common shares and common share purchase warrants of Cenovus. In addition, all of the issued and outstanding Husky preferred shares were exchanged for Cenovus preferred shares with substantially identical terms. The Arrangement closed on January 1, 2021 (see Note 39). The Arrangement will combine oil sands and heavy oil assets with extensive transportation, storage and logistics and downstream infrastructure, creating opportunities to optimize the margin captured across the heavy oil value chain. The combined company will be largely integrated reducing exposure to Alberta heavy oil price differentials while maintaining exposure to global commodity prices. Management has determined the operating segments based on information regularly reviewed for the purposes of decision making, allocating resources and assessing operational performance by Cenovus’s chief operating decision makers. The Company evaluates the financial performance of its operating segments primarily based on operating margin. The Company’s reportable segments at December 31, 2020 are: • Oil Sands , which includes the development and production of bitumen in northeast Alberta. Cenovus’s bitumen assets include Foster Creek, Christina Lake and Narrows Lake as well as other projects in the early stages of development. • Conventional , which includes assets rich in NGLs and natural gas within the Elmworth-Wapiti, Kaybob-Edson, and Clearwater operating areas in Alberta and British Columbia and the exploration for heavy oil in Marten Hills area. The assets include interests in numerous natural gas processing facilities. The Company renamed its Deep Basin segment to Conventional in 2020 and its new resource play, Marten Hills, was reclassified from the Oil Sands segment to the Conventional segment. Comparative periods have been reclassified. On December 2, 2020, the Company completed the sale of its Marten Hills assets (see Note 8). • Refining and Marketing , which is responsible for transporting, selling and refining crude oil into petroleum and chemical products. Cenovus jointly owns two refineries in the U.S. with the operator Phillips 66, an unrelated U.S. public company. In addition, Cenovus owns and operates a crude-by-rail terminal in Alberta. This segment coordinates Cenovus’s marketing and transportation initiatives to optimize product mix, delivery points, transportation commitments and customer diversification. The marketing of crude oil and natural gas sourced from Canada, including physical product sales that settle in the U.S., is considered to be undertaken by a Canadian business. U.S. sourced crude oil and natural gas purchases and sales are attributed to the U.S. • Corporate and Eliminations , which primarily includes unrealized gains and losses recorded on derivative financial instruments, gains and losses on divestiture of assets, as well as other Cenovus-wide costs for general and administrative, financing activities and research costs. As financial instruments are settled, the realized gains and losses are recorded in the reportable segment to which the derivative instrument relates. Eliminations include adjustments for internal usage of natural gas production between segments, transloading services provided to the Oil Sands segment by the Company’s rail terminal, crude oil production used as feedstock by the Refining and Marketing segment, and unrealized intersegment profits in inventory. Eliminations are recorded at transfer prices based on current market prices. The Corporate and Eliminations segment is attributed to Canada, with the exception of unrealized risk management gains and losses, which have been attributed to the country in which the transacting entity resides. The following tabular financial information presents the segmented information first by segment, then by product and geographic location. A) Results of Operations – Segment and Operational Information Oil Sands Conventional Refining and Marketing For the years ended December 31, 2020 2019 2018 2020 2019 2018 2020 2019 2018 Revenues Gross Sales 7,514 10,838 10,026 635 691 904 6,051 10,513 11,183 Less: Royalties 324 1,143 473 40 30 73 - - - 7,190 9,695 9,553 595 661 831 6,051 10,513 11,183 Expenses Purchased Product - - - - - - 5,397 8,795 9,201 Transportation and Blending 4,399 5,152 5,879 81 82 90 - - - Operating 1,094 1,039 1,037 318 337 403 824 948 927 Inventory Write-Down (Reversal) 316 - - - - - 239 49 60 (Gain) Loss on Risk Management 268 23 1,551 - - 26 (21 ) (16 ) (1 ) Operating Margin 1,113 3,481 1,086 196 242 312 (388 ) 737 996 Depreciation, Depletion and Amortization 1,684 1,543 1,439 880 319 412 739 280 222 Exploration Expense 9 18 6 82 64 2,117 - - - Segment Income (Loss) (580 ) 1,920 (359 ) (766 ) (141 ) (2,217 ) (1,127 ) 457 774 Corporate and Eliminations Consolidated For the years ended December 31, 2020 2019 2018 2020 2019 2018 Revenues Gross Sales (609 ) (689 ) (724 ) 13,591 21,353 21,389 Less: Royalties - - - 364 1,173 546 (609 ) (689 ) (724 ) 13,227 20,180 20,843 Expenses Purchased Product (278 ) (417 ) (517 ) 5,119 8,378 8,684 Transportation and Blending (36 ) (50 ) (27 ) 4,444 5,184 5,942 Operating (306 ) (236 ) (183 ) 1,930 2,088 2,184 Inventory Write-Down (Reversal) - - - 555 49 60 (Gain) Loss on Risk Management 61 149 (1,271 ) 308 156 305 Depreciation, Depletion and Amortization 161 107 58 3,464 2,249 2,131 Exploration Expense - - - 91 82 2,123 Segment Income (Loss) (211 ) (242 ) 1,216 (2,684 ) 1,994 (586 ) General and Administrative 292 331 1,020 292 331 1,020 Finance Costs 536 511 627 536 511 627 Interest Income (9 ) (12 ) (19 ) (9 ) (12 ) (19 ) Transaction Costs 29 - - 29 - - Foreign Exchange (Gain) Loss, Net (181 ) (404 ) 854 (181 ) (404 ) 854 Re-measurement of Contingent Payment (80 ) 164 50 (80 ) 164 50 (Gain) Loss on Divestiture of Assets (81 ) (2 ) 795 (81 ) (2 ) 795 Other (Income) Loss, Net 40 9 13 40 9 13 546 597 3,340 546 597 3,340 Earnings (Loss) From Continuing Operations Before Income Tax (3,230 ) 1,397 (3,926 ) Income Tax Expense (Recovery) (851 ) (797 ) (1,010 ) Net Earnings (Loss) From Continuing Operations (2,379 ) 2,194 (2,916 ) B) Revenues by Product For the years ended December 31, 2020 2019 2018 Upstream Crude Oil 7,270 9,790 9,662 NGLs 142 202 333 Natural Gas 315 299 320 Other 58 65 69 Refined Products 4,734 8,291 9,032 Market Optimization 1,317 2,222 2,151 Corporate and Eliminations (609 ) (689 ) (724 ) Revenues From Continuing Operations 13,227 20,180 20,843 C) Geographical Information Revenues For the years ended December 31, 2020 2019 2018 Canada 8,399 11,798 11,694 United States 4,828 8,382 9,149 Consolidated 13,227 20,180 20,843 Non-Current Assets (1) As at December 31, 2020 2019 Canada 26,168 28,336 United States 3,590 4,093 Consolidated 29,758 32,429 (1) Includes exploration and evaluation (“E&E”) assets, property, plant and equipment (“PP&E”), right-of-use (“ROU”) assets, other assets and goodwill. Export Sales Sales of crude oil, NGLs and natural gas produced or purchased in Canada that have been delivered to customers outside of Canada were $ 2,639 Major Customers In connection with the marketing and sale of Cenovus’s own and purchased crude oil, NGLs, natural gas and refined products for the year ended December 31, 2020, Cenovus had three 4,323 1,472 D) Assets by Segment E&E Assets (1) PP&E ROU Assets As at December 31, 2020 2019 2020 2019 2020 2019 Oil Sands 617 594 19,748 20,924 623 768 Conventional 6 193 1,758 2,433 3 3 Refining and Marketing - - 3,652 4,131 79 77 Corporate and Eliminations - - 253 346 434 477 Consolidated 623 787 25,411 27,834 1,139 1,325 Goodwill Total Assets As at December 31, 2020 2019 2020 2019 Oil Sands 2,272 2,272 24,656 26,203 Conventional - - 1,953 2,754 Refining and Marketing - - 4,951 5,688 Corporate and Eliminations - - 1,210 1,068 Consolidated 2,272 2,272 32,770 35,713 (1) Prior to its sale, Marten Hills was reclassified from the Oil Sands segment to the Conventional segment and the comparative period was reclassified. E) Capital Expenditures (1) For the years ended December 31, 2020 2019 2018 Capital Investment (2) Oil Sands 427 656 870 Conventional 78 103 228 Refining and Marketing 276 280 208 Corporate and Eliminations 60 137 57 841 1,176 1,363 Acquisition Capital Oil Sands 6 2 319 Conventional 12 7 22 Refining and Marketing - 4 - Total Capital Expenditures 859 1,189 1,704 (1) Includes expenditures on PP&E and E&E assets. (2 ) Prior to its sale, Marten Hills was reclassified from the Oil Sands segment to the Conventional segment and the comparative periods were reclassified.

Basis of Preparation and Statem

Basis of Preparation and Statement of Compliance	12 Months Ended
	Dec. 31, 2020
Basis Of Preparation And Statement Of Compliance [Abstract]
Basis of Preparation and Statement of Compliance	2. BASIS OF PREPARATION AND STATEMENT OF COMPLIANCE In these Consolidated Financial Statements, unless otherwise indicated, all dollars are expressed in Canadian dollars. All references to C$ or $ are to Canadian dollars and references to US$ are to U.S. dollars. These Consolidated Financial Statements have been prepared in accordance with International Financial Reporting Standards (“IFRS”) as issued by the International Accounting Standards Board (“IASB”) and interpretations of the International Financial Reporting Interpretations Committee (“IFRIC”). These Consolidated Financial Statements have been prepared on a historical cost basis, except as detailed in the Company’s accounting policies disclosed in Note 3. These Consolidated Financial Statements were approved by the Board of Directors on February 8, 2021.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2020
Disclosure Of Summary Of Significant Accounting Policies [Abstract]
Summary of Significant Accounting Policies	3. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES A) Principles of Consolidation The Consolidated Financial Statements include the accounts of Cenovus and its subsidiaries. Subsidiaries are entities over which the Company has control. Subsidiaries are consolidated from the date of acquisition of control and continue to be consolidated until the date that there is a loss of control. All intercompany transactions, balances, and unrealized gains and losses from intercompany transactions are eliminated on consolidation. Interests in joint arrangements are classified as either joint operations or joint ventures, depending on the rights and obligations of the parties to the arrangement. Joint operations arise when the Company has rights to the assets and obligations for the liabilities of the arrangement. The Company’s refining activities are conducted through the joint operation WRB Refining LP (“WRB”) and, accordingly, the accounts reflect the Company’s share of the assets, liabilities, revenues and expenses. An associate is an entity for which the Company has significant influence over but does not control or jointly control the investee. Investments in associates are accounted for using the equity method of accounting and are recognized at cost and adjusted thereafter to recognize the Company’s share of the investee’s profit or loss and other comprehensive income (“OCI”). B) Foreign Currency Translation Functional and Presentation Currency The Company’s functional and presentation currency is Canadian dollars. The accounts of the Company’s foreign operations that have a functional currency different from the Company’s presentation currency are translated into the Company’s presentation currency at period-end exchange rates for assets and liabilities, and using average rates over the period for revenues and expenses. Translation gains and losses relating to the foreign operations are recognized in OCI as cumulative translation adjustments. When the Company disposes of an entire interest in a foreign operation or loses control, joint control, or significant influence over a foreign operation, the foreign currency gains or losses accumulated in OCI related to the foreign operation are recognized in net earnings. When the Company disposes of part of an interest in a foreign operation that continues to be a subsidiary, a proportionate amount of gains and losses accumulated in OCI is allocated between controlling and non-controlling interests. Transactions and Balances Transactions in foreign currencies are translated to the respective functional currencies at exchange rates in effect at the dates of the transactions. C) Revenue Recognition Revenue is measured based on the consideration specified in a contract with a customer and excludes amounts collected on behalf of third parties. Cenovus recognizes revenue when it transfers control of the product or service to a customer, which is generally when title passes from the Company to its customer. Purchases and sales of products that are entered into in contemplation of each other with the same counterparty are recorded on a net basis. Revenues associated with services provided as agent are recorded as the services are provided. Cenovus recognizes revenue from the following major products and services: • Sale of crude oil, NGLs and natural gas. • Sale of petroleum and refined products. • Natural gas processing revenue. • Marketing and transportation services. • Fee-for-service hydrocarbon trans-loading services. The Company satisfies its performance obligations in contracts with customers upon the delivery of crude oil, NGLs, natural gas and petroleum and refined products, which is generally at a point in time. Performance obligations for natural gas processing revenue, marketing, transportation services and trans-loading services are satisfied over time as the service is provided. Cenovus sells its production of crude oil, NGLs, natural gas and petroleum and refined products generally pursuant to variable price contracts. The transaction price for variable price contracts is based on the commodity price, adjusted for quality, location and other factors. The amount of revenue recognized is based on the agreed transaction price with any variability in transaction price recognized in the same period. Revenue associated with natural gas processing, marketing, transportation services and trans-loading services are based, generally on fixed price contracts. Cenovus’s revenue transactions do not contain significant financing components and payments are typically due within 30 days of revenue recognition. The Company does not adjust transaction prices for the effects of a significant financing component when the period between the transfer of the promised goods or services to the customer and payment by the customer is less than one year. The Company does not disclose or quantify information about remaining performance obligations that have an original expected duration of one year or less and it does not have any long-term contracts with unfulfilled performance obligations. D) Transportation and Blending The costs associated with the transportation of crude oil, NGLs and natural gas, including the cost of diluent used in blending, are recognized when the product is sold. E) Exploration Expense Costs incurred prior to obtaining the legal right to explore (pre-exploration costs) are expensed in the period in which they are incurred as exploration expense. Costs incurred after the legal right to explore is obtained are initially capitalized. If it is determined that the field/project/area is not technically feasible and commercially viable or if the Company decides not to continue the exploration and evaluation activity, the unrecoverable accumulated costs are expensed as exploration expense. F) Employee Benefit Plans The Company provides employees with a pension plan that includes either a defined contribution or defined benefit component and an other post-employment benefit plan (“OPEB”). Pension expense for the defined contribution pension is recorded as the benefits are earned. The cost of the defined benefit pension and OPEB plans are actuarially determined using the projected unit credit method. The amount recognized in other liabilities on the Consolidated Balance Sheets for the defined benefit pension and OPEB plans is the present value of the defined benefit obligation less the fair value of plan assets. Any surplus resulting from this calculation is limited to the present value of any economic benefits available in the form of refunds from the plans or reductions in future contributions to the plans. Changes in the defined benefit obligation from service costs, net interest and remeasurements are recognized as follows: • Service costs, including current service costs, past service costs, gains and losses on curtailments, and settlements, are recorded with pension benefit costs. • Net interest is calculated by applying the same discount rate used to measure the defined benefit obligation at the beginning of the annual period to the net defined benefit asset or liability measured. Interest expense and interest income on net post-employment benefit liabilities and assets are recorded with pension benefit costs in operating, and general and administrative expenses, as well as PP&E and E&E assets. • Remeasurements, composed of actuarial gains and losses, the effect of changes to the asset ceiling (excluding interest) and the return on plan assets (excluding interest income), are charged or credited to equity in OCI in the period in which they arise. Remeasurements are not reclassified to net earnings in subsequent periods. Pension benefit costs are recorded in operating, and general and administrative expenses, as well as PP&E and E&E assets, corresponding to where the associated salaries of the employees rendering the service are recorded. From time-to-time, the Company may provide certain other long-term incentive benefits to employees. In 2019, a one-time incentive program was introduced whereby a cash award equivalent to the employee’s base salary is payable if Cenovus achieves prior to February 12, 2024 a target share price of $20 per share for a period of 20 consecutive trading days on the TSX (the “Plan”). All employees, except for the President & Chief Executive Officer, are eligible and new employees are eligible for a pro-rated award based on start date provided they are employed on the payout date. The obligation related to this Plan is estimated as the probability of the payout being achieved multiplied by the expected payout amount. The obligation is recognized over the greater of (i) the time to earliest payout of February 13, 2022; and (ii) the estimated time until payout is achieved, prior to February 12, 2024 as general and administrative expense. G) Government Grants Government grants are recognized when there is reasonable assurance that the grant will be received and all conditions associated with the grant are met. Grants related to assets are recorded as a reduction to the asset’s carrying value and are depreciated over the useful life of the asset. Claims under government grant programs related to income are recorded as other income in the period in which eligible expenses were incurred or when the services have been performed. H) Income Taxes Income taxes comprise current and deferred taxes. Income taxes are provided for on a non-discounted basis at amounts expected to be paid using the tax rates and laws that have been enacted or substantively enacted at the Consolidated Balance Sheet date. Cenovus follows the liability method of accounting for income taxes, where deferred income taxes are recorded for the effect of any temporary difference between the accounting and income tax basis of an asset or liability, using the substantively enacted income tax rates expected to apply when the assets are realized or liabilities are settled. Deferred income tax balances are adjusted to reflect changes in income tax rates that are substantively enacted with the adjustment being recognized in net earnings in the period that the change occurs, except when it relates to items charged or credited directly to equity or OCI, in which case the deferred income tax is also recorded in equity or OCI, respectively. Deferred income tax is recognized on temporary differences arising from investments in subsidiaries except in the case where the timing of the reversal of the temporary difference is controlled by the Company and it is probable that the temporary difference will not reverse in the foreseeable future or when distributions can be made without incurring income taxes. Deferred income tax assets are recognized only to the extent that it is probable that future taxable profit will be available against which the temporary differences can be utilized. Deferred income tax assets and liabilities are only offset where they arise within the same entity and tax jurisdiction. Deferred income tax assets and liabilities are presented as non-current. I) Net Earnings per Share Amounts Basic net earnings per share is computed by dividing net earnings by the weighted average number of common shares outstanding during the period. Diluted net earnings per share is calculated giving effect to the potential dilution that would occur if stock options or other contracts to issue common shares were exercised or converted to common shares. The treasury stock method is used to determine the dilutive effect of stock options and other dilutive instruments. The treasury stock method assumes that proceeds received from the exercise of in-the-money stock options are used to repurchase common shares at the average market price. For those contracts that may be settled in cash or in shares at the holder’s option, the more dilutive of cash settlement and share settlement is used in calculating diluted earnings per share. J) Cash and Cash Equivalents Cash and cash equivalents include short-term investments, such as money market deposits or similar type instruments, with a maturity of three months or less. K) Inventories Product inventories are valued at the lower of cost and net realizable value on a first-in, first-out or weighted average cost basis. The cost of inventory includes all costs incurred in the normal course of business to bring each product to its present location and condition. Net realizable value is the estimated selling price in the ordinary course of business less any expected selling costs. If the carrying amount exceeds net realizable value, a write-down is recognized. The write-down may be reversed in a subsequent period if circumstances which caused it no longer exist and the inventory is still on hand. L) Exploration and Evaluation Assets Costs incurred after the legal right to explore an area has been obtained, and before technical feasibility and commercial viability of the field/project/area have been established, are capitalized as E&E assets. These costs include license acquisition, geological and geophysical, drilling, sampling, decommissioning and other directly attributable internal costs. E&E assets are carried forward until technical feasibility and commercial viability of the field/project/area is established or the assets are determined to be impaired or the future economic value has decreased. E&E costs are subject to regular technical, commercial and Management review to confirm the continued intent to develop the resources. Assets classified as E&E may have sales of crude oil, NGLs or natural gas prior to the reclassification to PP&E. These operating results are recognized in the Consolidated Statements of Earnings (Loss). A depletion charge, recorded as depreciation, depletion and amortization (“DD&A”), is recognized on this production using a unit-of-production method based on estimated proved reserves determined using forward prices and costs and considering any estimated future costs to be incurred in developing the proved reserves. Natural gas reserves are converted on an energy equivalent basis. Non-producing assets classified as E&E are not depleted. Once technical feasibility and commercial viability have been established, the carrying value of the E&E asset is tested for impairment. The carrying value, net of any impairment loss, is then reclassified as PP&E. Any gains or losses from the divestiture of E&E assets are recognized in net earnings. M) Property, Plant and Equipment General PP&E is stated at cost less accumulated DD&A, and net of any impairment losses. Expenditures related to renewals or betterments that improve the productive capacity or extend the life of an asset are capitalized. Maintenance and repairs are expensed as incurred. Land is not depreciated. Any gains or losses from the divestiture of PP&E are recognized in net earnings. Development and Production Assets Development and production assets are capitalized on an area-by-area basis and include all costs associated with the development and production of crude oil and natural gas properties, as well as any E&E expenditures incurred in finding reserves of crude oil, NGLs or natural gas transferred from E&E assets. Capitalized costs include directly attributable internal costs, decommissioning liabilities and, for qualifying assets, borrowing costs directly associated with the acquisition of, the exploration for, and the development of crude oil and natural gas reserves. Costs accumulated within each area are depleted using the unit-of-production method based on estimated proved reserves determined using forward prices and costs. For the purpose of this calculation, natural gas is converted to crude oil on an energy equivalent basis. Costs subject to depletion include estimated future costs to be incurred in developing proved reserves. Exchanges of development and production assets are measured at fair value unless the transaction lacks commercial substance or the fair value of neither the asset received, nor the asset given up, can be reliably measured. When fair value is not used, the carrying amount of the asset given up is used as the cost of the asset acquired. Other Upstream Assets Other upstream assets include information technology assets used to support the upstream business. These assets are depreciated on a straight-line basis over their useful lives of three years. Other upstream assets also include gross overriding royalty interests (“GORRs”) in certain oil and gas properties and are depleted using a unit-of-production method. Refining Assets The initial acquisition costs of refining PP&E are capitalized when incurred. Costs include the cost of constructing or otherwise acquiring the equipment or facilities, the cost of installing the asset and making it ready for its intended use, the associated decommissioning costs and, for qualifying assets, borrowing costs. Refining assets are depreciated on a straight-line basis over the estimated service life of each component of the refinery. The major components are depreciated as follows: Land improvements and buildings 25 to 40 years Office equipment and vehicles 3 to 15 years Refining equipment 10 to 60 years The residual value, the method of amortization and the useful life of each component are reviewed annually and adjusted on a prospective basis, if appropriate. Other Assets Costs associated with the crude-by-rail terminal, infrastructure, office furniture, fixtures, leasehold improvements, information technology and aircraft are carried at cost and depreciated on a straight-line basis over the estimated service lives of the assets, which range from three years to 60 years. The residual value, the method of amortization and the useful lives of the assets are reviewed annually and adjusted on a prospective basis, if appropriate. N) Impairment of Non-Financial Assets PP&E, E&E assets and ROU assets are reviewed separately for indicators of impairment quarterly or when facts and circumstances suggest that the carrying amount may exceed its recoverable amount. Goodwill is tested for impairment at least annually. If indicators of impairment exist, the recoverable amount of the asset or cash-generating unit (“CGU”) is estimated as the greater of value-in-use (“VIU”) and fair value less costs of disposal (“FVLCOD”). VIU is estimated as the present value of the future cash flows expected to arise from the continuing use of a CGU or an asset. FVLCOD is the amount that would be realized from the disposition of an asset or CGU in an arm’s length transaction between knowledgeable and willing parties. For Cenovus’s upstream assets, FVLCOD is based on the discounted after-tax cash flows of reserves and resources using forward prices and costs, consistent with Cenovus’s independent qualified reserves evaluators (“IQREs”) and may consider an evaluation of comparable asset transactions. E&E assets are allocated to a related CGU containing development and production assets for the purposes of testing for impairment. ROU assets may be tested as part of a CGU, as a separate CGU or as an individual asset. Goodwill is allocated to the CGUs to which it contributes to the future cash flows. If the recoverable amount of the CGU is less than the carrying amount, an impairment loss is recognized. An impairment loss is allocated first to reduce the carrying amount of any goodwill allocated to the CGU and then to reduce the carrying amounts of the other assets in the CGU. Goodwill impairments are not reversed. Impairment losses on PP&E and ROU assets are recognized in the Consolidated Statements of Earnings (Loss) as additional DD&A and E&E asset impairments or write-downs are recognized as exploration expense. Impairment losses recognized in prior periods, other than goodwill impairments, are assessed at each reporting date for any indicators that the impairment losses may no longer exist or may have decreased. In the event that an impairment loss reverses, the carrying amount of the asset is increased to the revised estimate of its recoverable amount, but only to the extent that the carrying amount does not exceed the amount that would have been determined had no impairment loss been recognized on the asset in prior periods. The amount of the reversal is recognized in net earnings. O) Leases The Company adopted IFRS 16, “ Lease Policy Applicable From January 1, 2019 Leases The Company assesses whether a contract is a lease based on whether the contract conveys the right to control the use of an underlying asset for a period of time in exchange for consideration. The Company allocates the consideration in the contract to each lease component on the basis of their relative stand-alone prices. However, for the leases of storage tanks, the Company has elected not to separate non-lease components. As Lessee Leases are recognized as a ROU asset and a corresponding lease liability at the date on which the leased asset is available for use by the Company. Assets and liabilities arising from a lease are initially measured on a present value basis. Lease liabilities include the net present value of fixed payments, costs to be incurred by the lessee in dismantling, removing and restoring the underlying asset, variable lease payments that are based on an index or a rate, amounts expected to be paid by the lessee under residual value guarantees, the exercise price of purchase options if the lessee is reasonably certain to exercise that option, and payments of penalties for terminating the lease, less any lease incentives receivable. These payments are discounted using the Company’s incremental borrowing rate when the rate implicit in the lease is not readily available. The Company uses a single discount rate for a portfolio of leases with reasonably similar characteristics. Lease payments are allocated between the liability and finance costs. The finance cost is charged to net earnings over the lease term. The lease liability is measured at amortized cost using the effective interest method. It is remeasured when there is a change in the future lease payments arising from a change in an index or rate, if there is a change in the amount expected to be payable under a residual value guarantee or if there is a change in the assessment of whether the Company will exercise a purchase, extension or termination option that is within the control of the Company. When the lease liability is remeasured, a corresponding adjustment is made to the carrying amount of the ROU asset or is recorded in the Consolidated Statements of Earnings (Loss) if the carrying amount of the ROU asset has been reduced to zero. The ROU asset is initially measured at cost, which comprises the initial amount of the lease liability any initial direct costs incurred and an estimate of costs to dismantle and remove the underlying asset or to restore the underlying asset or site on which it is located less any lease payments made at or before the commencement date. The ROU asset is depreciated, on a straight-line basis, over the shorter of the estimated useful life of the asset or the lease term. The ROU asset may be adjusted for certain remeasurements of the lease liability and impairment losses. Leases that have terms of less than twelve months or leases on which the underlying asset is of low value are recognized as an expense in the Consolidated Statements of Earnings (Loss) on a straight-line basis over the lease term. A lease modification will be accounted for as a separate lease if the modification increases the scope of the lease and if the consideration for the lease increases by an amount commensurate with the stand-alone price for the increase in scope. For a modification that is not a separate lease or where the increase in consideration is not commensurate, at the effective date of the lease modification, the Company will remeasure the lease liability using the Company’s incremental borrowing rate, when the rate implicit to the lease is not readily available, with a corresponding adjustment to the ROU asset. A modification that decreases the scope of the lease will be accounted for by decreasing the carrying amount of the ROU asset, and recognizing a gain or loss in net earnings that reflects the proportionate decrease in scope. As Lessor As a lessor, the Company assesses at inception whether a lease is a finance or operating lease. Leases where the Company transfers substantially all of the risk and rewards incidental to ownership of the underlying asset are classified as financing leases. Under a finance lease, the Company recognizes a receivable at an amount equal to the net investment in the lease which is the present value of the aggregate of lease payments receivable by the lessor. If substantially all the risks and rewards of ownership of an asset are not transferred the lease is classified as an operating lease. The Company recognizes lease payments received under operating leases as income on a straight-line basis over the lease term as other income. When the Company is an intermediate lessor, it accounts for its interest in the head lease and the sublease separately. It assesses the lease classification of a sublease with reference to the ROU asset from the head lease not with reference to the underlying assets. If the head lease is a short-term lease to which the Company applies the exemption for lease accounting, the sublease is classified as an operating lease. Policy Applicable Before January 1, 2019 Leases in which substantially all of the risks and rewards of ownership are retained by the lessor are classified as operating leases. Operating lease payments are recognized as an expense on a straight-line basis over the lease term. Leases where the Company assumes substantially all the risks and rewards of ownership are classified as finance leases. At inception, a leased asset within PP&E and a corresponding lease obligation are recognized. The leased asset is depreciated over the shorter of the estimated useful life of the asset or the lease term. P) Intangible Assets Intangible assets acquired separately are initially measured at cost. Following initial recognition, intangible assets are recognized at cost less any accumulated amortization and accumulated impairment losses. Intangible assets with finite lives are amortized over the useful life and assessed for impairment whenever there is an indication that the intangible asset may be impaired. The amortization expense on intangible assets is recognized in the Q) Business Combinations and Goodwill Business combinations are accounted for using the acquisition method of accounting in which the identifiable assets acquired, liabilities assumed and non-controlling interest, if any, are recognized and measured at their fair value at the date of acquisition, with the exception of income taxes, stock-based compensation, lease liabilities and ROU assets. Any excess of the purchase price plus any non-controlling interest over the value of the net assets acquired is recognized as goodwill. Any deficiency of the purchase price over the value of the net assets acquired is credited to net earnings. At acquisition, goodwill is allocated to each of the CGUs to which it relates. Subsequent measurement of goodwill is at cost less any accumulated impairment losses. Contingent consideration transferred in a business combination is measured at fair value on the date of acquisition and classified as a financial liability or equity. Contingent consideration classified as a liability is re-measured at fair value at each reporting date, with changes in fair value recognized in net earnings. Payments are classified as cash used in investing activities until the cumulative payments exceed the acquisition date fair value of the liability. Cumulative payments in excess of the acquisition date fair value are classified as cash used in operating activities. Contingent consideration classified as equity are not re-measured and settlements are accounted for within equity. When a business combination is achieved in stages, the Company re-measures its pre-existing interest at the acquisition date fair value and recognizes the resulting gain or loss, if any, in net earnings. R) Provisions General A provision is recognized if, as a result of a past event, the Company has a present obligation, legal or constructive, that can be estimated reliably, and it is more likely than not that an outflow of economic benefits will be required to settle the obligation. Where applicable, provisions are determined by discounting the expected future cash flows at a pre-tax credit-adjusted rate that reflects the current market assessments of the time value of money and the risks specific to the liability. The increase in the provision due to the passage of time is recognized as a finance cost in the Consolidated Statements of Earnings (Loss). Decommissioning Liabilities Decommissioning liabilities include those legal or constructive obligations where the Company will be required to retire tangible long-lived assets such as producing well sites, upstream processing facilities, refining facilities and the crude-by-rail terminal. The amount recognized is the present value of estimated future expenditures required to settle the obligation using a credit-adjusted risk-free rate. A corresponding asset equal to the initial estimate of the liability is capitalized as part of the cost of the related long-lived asset. Changes in the estimated liability resulting from revisions to expected timing or future decommissioning costs are recognized as a change in the decommissioning liability and the related long-lived asset. The amount capitalized in PP&E is depreciated over the useful life of the related asset. Actual expenditures incurred are charged against the accumulated liability. Onerous Contract Provisions Onerous contract provisions are recognized when the unavoidable costs of meeting the obligation exceed the economic benefit derived from the contract. The provision for onerous contracts is measured at the present value of estimated future cash flows underlying the obligations less any estimated recoveries, discounted at the credit-adjusted risk-free rate. Changes in the underlying assumptions are recognized in the Consolidated Statements of Earnings (Loss). S) Share Capital Common shares are classified as equity. Transaction costs directly attributable to the issue of common shares are recognized as a deduction from equity, net of any income taxes. T) Stock-Based Compensation Net Settlement Rights NSRs are accounted for as equity instruments, which are measured at fair value on the grant date using the Black-Scholes-Merton valuation model and are not revalued at each reporting date. The fair value is recognized as stock-based compensation costs over the vesting period, with a corresponding increase recorded as paid in surplus in Shareholders’ Equity. On exercise, the cash consideration received by the Company and the associated paid in surplus are recorded as share capital. PSUs, RSUs and DSUs are accounted for as liability instruments and are measured at fair value based on the market value of Cenovus’s common shares at each period end. The fair value is recognized as stock-based compensation costs over the vesting period. Fluctuations in the fair values are recognized as stock-based compensation costs in the period they occur. U) Financial Instruments The Company’s financial assets include cash and cash equivalents, accounts receivable and accrued revenues, risk management assets, net investment in finance leases, investments in the equity of private companies and long-term receivables. The Company’s financial liabilities include accounts payable and accrued liabilities, short-term borrowings, lease liabilities, contingent payment, risk management liabilities and long-term debt. Financial instruments are recognized when the Company becomes a party to the contractual provisions of the instrument. Financial assets and liabilities are not offset unless the Company has the current legal right to offset and intends to settle on a net basis or settle the asset and liability simultaneously. The Company characterizes its fair value measurements into a three-level hierarchy depending on the degree to which the inputs are observable, as follows: • Level 1 inputs are quoted prices in active markets for identical assets and liabilities. • Level 2 inputs are inputs, other than quoted prices included within Level 1, that are observable for the asset or liability either directly or indirectly. • Level 3 inputs are unobservable inputs for the asset or liability. Classification and Measurement of Financial Assets The i

Critical Accounting Judgments,

Critical Accounting Judgments, Key Sources of Estimation Uncertainty and Recent Development	12 Months Ended
	Dec. 31, 2020
Disclosure Of Accounting Judgements And Estimates [Abstract]
Critical Accounting Judgments and Key Sources of Estimation Uncertainty	4. CRITICAL ACCOUNTING JUDGMENTS AND KEY SOURCES OF ESTIMATION UNCERTAINTY The timely preparation of the Consolidated Financial Statements in accordance with IFRS requires that Management make estimates and assumptions, and use judgment regarding the reported amounts of assets and liabilities, and disclosures of contingent assets and liabilities at the date of the Consolidated Financial Statements, and the reported amounts of revenues and expenses during the period. Such estimates primarily relate to unsettled transactions and events as of the date of the Consolidated Financial Statements. The estimated fair value of financial assets and liabilities, by their very nature, are subject to measurement uncertainty. Accordingly, actual results may differ from estimated amounts as future confirming events occur. A) Critical Judgments in Applying Accounting Policies Critical judgments are those judgments made by Management in the process of applying accounting policies that have the most significant effect on the amounts recorded in the Company’s Consolidated Financial Statements. Joint Arrangements The classification of a joint arrangement as either a joint operation or a joint venture requires judgment. Cenovus holds a 50 percent interest in WRB, a jointly controlled entity. It was determined that Cenovus has the rights to the assets and obligations for the liabilities of WRB. As a result, the joint arrangement is classified as a joint operation and the Company’s share of the assets, liabilities, revenues and expenses are recorded in the Consolidated Financial Statements. In determining the classification of its joint arrangements under IFRS 11, “ Joint Arrangements • The intention of the joint arrangement was to form an integrated North American heavy oil business. The integrated business was structured, initially on a tax neutral basis, through two partnerships due to the assets residing in different tax jurisdictions. Partnerships are “flow-through” entities which have a limited life. • The partnership agreements require the partners (Cenovus and Phillips 66 or respective subsidiaries) to make contributions if funds are insufficient to meet the obligations or liabilities of the partnerships. The past and future development of WRB is dependent on funding from the partners by way of partnership notes payable and loans. • The WRB working interest relationship is operated whereby the operating partner takes product on behalf of the participants and is modified to account for the operating environment of the refining business. • Phillips 66, as the operator, either directly or through wholly-owned subsidiaries, provide marketing services, purchase necessary feedstock, and arrange for transportation and storage on the partners’ behalf as the agreements prohibit the partnership from undertaking these roles themselves. In addition, the partnership does not have employees and, as such, are not capable of performing these roles. • In the arrangement, output is taken by the partners, indicating that the partners have the rights to the economic benefits of the assets and the obligation for funding the liabilities of the arrangement. Exploration and Evaluation Assets The application of the Company’s accounting policy for E&E expenditures requires judgment in determining whether it is likely that future economic benefit exists when activities have not reached a stage where technical feasibility and commercial viability can be reasonably determined. Factors such as drilling results, future capital programs, future operating expenses, as well as estimated reserves and resources are considered. In addition, Management uses judgment to determine when E&E assets are reclassified to PP&E. In making this determination, various factors are considered, including the existence of reserves, and whether the appropriate approvals have been received from regulatory bodies and the Company’s internal approval process. Identification of Cash-Generating Units CGUs are defined as the lowest level of integrated assets for which there are separately identifiable cash flows that are largely independent of cash flows from other assets or groups of assets. The classification of assets and allocation of corporate assets into CGUs requires significant judgment and interpretation. Factors considered in the classification include the integration between assets, shared infrastructures, the existence of common sales points, geography, geologic structure, and the manner in which Management monitors and makes decisions about its operations. The recoverability of the Company’s upstream, refining, crude-by-rail, railcars, storage tanks and corporate assets are assessed at the CGU level. As such, the determination of a CGU could have a significant impact on impairment losses and reversals. Determining the Lease Term In determining the lease term, Management considers all facts and circumstances that create an economic incentive to exercise an extension option, or not exercise a termination option. The assessment is reviewed if a significant event or a significant change in circumstances occurs which affects this assessment. B) Key Sources of Estimation Uncertainty Critical accounting estimates are those estimates that require Management to make particularly subjective or complex judgments about matters that are inherently uncertain. Estimates and underlying assumptions are reviewed on an ongoing basis and any revisions to accounting estimates are recorded in the period in which the estimates are revised. The following are the key assumptions about the future and other key sources of estimation at the end of the reporting period that, if changed, could result in a material adjustment to the carrying amount of assets and liabilities within the next financial year. In March 2020, the World Health Organization declared a global pandemic following the emergence and rapid spread of a novel strain of the coronavirus (“COVID-19”). The outbreak and subsequent measures intended to limit the pandemic contributed to significant declines and volatility in financial markets. The pandemic has adversely impacted global commercial activity, including significantly reducing worldwide demand for crude oil. The full extent of the impact of COVID-19 on the Company’s operations and future financial performance is currently unknown. It will depend on future developments that are uncertain and unpredictable, including the duration and spread of COVID-19, its continued impact on capital and financial markets on a macro-scale and any new information that may emerge concerning the severity of the virus. These uncertainties may persist beyond when it is determined how to contain the virus or treat its impact. The outbreak presents uncertainty and risk with respect to the Company, its performance, and estimates and assumptions used by Management in the preparation of its financial results. The outbreak and current market conditions have increased the complexity of estimates and assumptions used to prepare the annual Consolidated Financial Statements, particularly related to recoverable amounts. In addition, the evolving worldwide demand for energy and global advancement of alternative sources of energy that are not sourced from fossil fuels could result in a change in assumptions used in determining the recoverable amount and could affect the carrying value of the related assets. The timing in which global energy markets transition from carbon-based sources to alternative energy is highly uncertain. Changes to assumptions could result in a material adjustment to the carrying amount of assets and liabilities within the next financial year. Crude Oil and Natural Gas Reserves There are a number of inherent uncertainties associated with estimating crude oil and natural gas reserves. Reserves estimates are dependent upon variables including the recoverable quantities of hydrocarbons, the cost of the development of the required infrastructure to recover the hydrocarbons, production costs, estimated selling price of the hydrocarbons produced, royalty payments and taxes. Changes in these variables could significantly impact the reserves estimates which would affect the impairment test recoverable amount and DD&A expense of the Company’s crude oil and natural gas assets in the Oil Sands and Conventional segments. The Company’s reserves are evaluated annually and reported to the Company by its IQREs. Recoverable Amounts Determining the recoverable amount of a CGU or an individual asset requires the use of estimates and assumptions, which are subject to change as new information becomes available. For the Company’s upstream assets, these estimates include forward commodity prices, expected production volumes, quantity of reserves and resources, discount rates, future development and operating expenses. Recoverable amounts for the Company’s refining assets, crude-by-rail terminal and related ROU assets use assumptions such as throughput, forward commodity prices, market crack spreads, operating expenses, transportation capacity, future capital expenditures, supply and demand conditions and the terminal values used. Recoverable amounts for the Company’s real estate ROU assets use assumptions such as real estate market conditions which includes market vacancy rates and sublease market conditions, price per square footage, real estate space availability and borrowing costs. Changes in assumptions used in determining the recoverable amount could affect the carrying value of the related assets. Decommissioning Costs Provisions are recorded for the future decommissioning and restoration of the Company’s upstream assets, refining assets and crude-by-rail terminal at the end of their economic lives. Management uses judgment to assess the existence and to estimate the future liability. The actual cost of decommissioning and restoration is uncertain and cost estimates may change in response to numerous factors including changes in legal requirements, technological advances, inflation and the timing of expected decommissioning and restoration. In addition, Management determines the appropriate discount rate at the end of each reporting period. This discount rate, which is credit-adjusted, is used to determine the present value of the estimated future cash outflows required to settle the obligation and may change in response to numerous market factors. Fair Value of Assets Acquired and Liabilities Assumed in a Business Combination The fair value of assets acquired and liabilities assumed in a business combination, including contingent consideration and goodwill, is estimated based on information available at the date of acquisition. Various valuation techniques are applied for measuring fair value including market comparables and discounted cash flows which rely on assumptions such as forward commodity prices, quantity of reserves and resources, production costs, Canadian-U.S. foreign exchange rates and discount rates. Changes in these variables could significantly impact the carrying value of the net assets. Income Tax Provisions Tax regulations and legislation and the interpretations thereof in the various jurisdictions in which Cenovus operates are subject to change. There are usually a number of tax matters under review; therefore, income taxes are subject to measurement uncertainty. Deferred income tax assets are recorded to the extent that it is probable that the deductible temporary differences will be recoverable in future periods. The recoverability assessment involves a significant amount of estimation including an evaluation of when the temporary differences will reverse, an analysis of the amount of future taxable earnings, the availability of cash flow to offset the tax assets when the reversal occurs and the application of tax laws. There are some transactions for which the ultimate tax determination is uncertain. To the extent that assumptions used in the recoverability assessment change, there may be a significant impact on the Consolidated Financial Statements of future periods.

General and Administrative

General and Administrative	12 Months Ended
	Dec. 31, 2020
General And Administrative Expenses [Abstract]
General and Administrative	5. GENERAL AND ADMINISTRATIVE For the years ended December 31, 2020 2019 2018 Salaries and Benefits 145 143 205 Administrative and Other 84 95 177 Onerous Contract Provisions (Recovery) 18 (5 ) 629 Stock-Based Compensation Expense (Note 32) 49 67 9 Other Long-Term Incentive Expense (Recovery) (4 ) 31 - 292 331 1,020

Finance Costs

Finance Costs	12 Months Ended
	Dec. 31, 2020
Finance Costs [Abstract]
Finance Costs	6. FINANCE COSTS For the years ended December 31, 2020 2019 2018 Interest Expense – Short-Term Borrowings and Long-Term Debt 392 407 516 Net (Discount) Premium on Redemption of Long-Term Debt (Note 24) (25 ) (63 ) 17 Interest Expense – Lease Liabilities (Note 25) 87 82 - Unwinding of Discount on Decommissioning Liabilities (Note 27) 57 58 62 Other 25 27 32 536 511 627

Foreign Exchange (Gain) Loss, N

Foreign Exchange (Gain) Loss, Net	12 Months Ended
	Dec. 31, 2020
Foreign Exchange Gains Losses [Abstract]
Foreign Exchange (Gain) Loss, Net	7. FOREIGN EXCHANGE (GAIN) LOSS, NET For the years ended December 31, 2020 2019 2018 Unrealized Foreign Exchange (Gain) Loss on Translation of: U.S. Dollar Debt Issued From Canada (194 ) (800 ) 602 Other 63 (27 ) 47 Unrealized Foreign Exchange (Gain) Loss (131 ) (827 ) 649 Realized Foreign Exchange (Gain) Loss (50 ) 423 205 (181 ) (404 ) 854

Divestitures

Divestitures	12 Months Ended
	Dec. 31, 2020
Gains Losses On Disposals Of Noncurrent Assets [Abstract]
Divestitures	8. DIVESTITURES On December 2, 2020, the Company sold its Marten Hills assets in northern Alberta to Headwater Exploration Inc. (“Headwater”) for total consideration of $ 138 97 at $8 million at the date of close. The share purchase warrants have retained a GORR in the Marten Hills assets which was reclassified from E&E to PP&E for $41 million On September 6, 2018, the Company completed the sale of Cenovus Pipestone Partnership (“CPP”), a wholly-owned subsidiary, for cash proceeds of $625 million, before closing adjustments. CPP held the Company’s Pipestone and Wembley natural gas and liquids business in northwestern Alberta and included the Company’s 39 percent operated working interest in the Wembley gas plant. A before-tax loss of $797 million was recorded on the sale (after-tax – $557 million).

Other (Income) Loss, Net

Other (Income) Loss, Net	12 Months Ended
	Dec. 31, 2020
Other Income Loss Net [Abstract]
Other (Income) Loss, Net	9. OTHER (INCOME) LOSS, NET For the year ended December 31, 2020, the Company recorded a $100 million loss related to the Keystone XL pipeline project. The Government of Canada passed the Canada Emergency Wage Subsidy (“CEWS”) as part of its COVID-19 Economic Response Plan. The program is effective from March 15, 2020 to June 2021. For the year ended December 31, 2020, the Company recorded $ 40 For the year ended December 31, 2020, the Company recognized $ 24

Impairment Charges and Reversal

Impairment Charges and Reversals	12 Months Ended
	Dec. 31, 2020
Disclosure Of Impairment Loss Recognised Or Reversed [Abstract]
Impairment Charges and Reversals	10. IMPAIRMENT CHARGES AND REVERSALS A) Cash-Generating Unit Net Impairments On a quarterly basis, the Company assesses its CGUs for indicators of impairment or when facts and circumstances suggest the carrying amount may exceed its recoverable amount. Goodwill is tested for impairment at least annually. 2020 Upstream Impairments During the three months ended March 31, 2020, the Company tested its upstream CGUs and CGUs with associated goodwill for impairment. As a result, the Company recorded an impairment loss of $315 million as additional DD&A in the Conventional segment due to the decline in forward crude oil and natural gas prices. As at March 31, 2020, there was no impairment of goodwill or Oil Sands CGUs. As at December 31, 2020, indicators of impairment were noted for the Company’s Conventional assets due to a change in future development plans since the Company last tested for impairment as at March 31, 2020. Therefore, the Company tested its Conventional CGUs for impairment and determined that the carrying amount was greater than the recoverable amount for certain CGUs and recorded an additional impairment loss of $ 240 For the purpose of impairment testing, goodwill is allocated to the CGU of which it relates. T was no impairment The following table summarizes the year ended December 31, 2020 impairment losses and estimated recoverable amounts as at December 31, 2020 by CGU: CGU Impairment Amount Recoverable Amount Clearwater 260 160 Elmworth-Wapiti 120 259 Kaybob-Edson 175 384 Key Assumptions The recoverable amounts (Level 3) of Cenovus’s upstream CGUs were determined based on FVLCOD. Key assumptions in the determination of future cash flows from reserves include crude oil, NGLs and natural gas prices, costs to develop and the discount rate. The fair values for producing properties were calculated based on discounted after-tax cash flows of proved and probable reserves using forward prices and cost estimates at December 31, 2020. All reserves have been evaluated as at December 31, 2020 by the Company’s IQREs. Crude Oil, NGLs and Natural Gas Prices The forward prices as at December 31, 2020, used to determine future cash flows from crude oil, NGLs and natural gas reserves were: 2021 2022 2023 2024 2025 Average Annual Increase Thereafter WTI (US$/barrel) (1) 47.17 50.17 53.17 54.97 56.07 2.0 % WCS (C$/barrel) (2) 44.63 48.18 52.10 54.10 55.19 2.0 % Edmonton C5+ (C$/barrel) 59.24 63.19 67.34 69.77 71.18 2.0 % AECO (C$/Mcf) (3) 2.88 2.80 2.71 2.75 2.80 2.0 % (1) West Texas Intermediate (“WTI”). (2) Western Canadian Select (“WCS”). (3) Alberta Energy Company (“AECO”) natural gas. Assumes gas heating value of one million British thermal units per thousand cubic feet (“Mcf”). Discount and Inflation Rates Discounted future cash flows are determined by applying a discount rate between 10 Sensitivities The sensitivity analysis below shows the impact that a change in the discount rate or forward commodity prices would have had on the calculated recoverable amount in the impairment testing completed as at December 31, 2020 for the following CGUs: Increase (Decrease) to Recoverable Amount One Percent Increase in the Discount Rate One Percent Decrease in the Discount Rate Five Percent Increase in the Forward Price Estimates Five Percent Decrease in the Forward Price Estimates Clearwater (5 ) 6 52 (97 ) Elmworth-Wapiti (7 ) 8 54 (96 ) Kaybob-Edson (13 ) 14 54 (106 ) 2020 Refining Impairments As at September 30, 2020, the recovery in demand for refined products from the impact of COVID-19 lagged expectations resulting in higher than anticipated inventory levels. These factors, along with low market crack spreads and crude oil processing runs for North American refineries, were identified as potential indicators of impairment for the Wood River and Borger CGUs. As at September 30, 2020, the carrying amount of the Borger CGU was determined to be greater than the recoverable amount and an impairment charge of $450 million was recorded as additional DD&A in the Refining and Marketing segment. The recoverable amount of the Borger CGU was estimated at $692 million, using a discounted cash flow method in accordance with IFRS. As at September 30, 2020, no impairment of the Wood River Key Assumptions The recoverable amount (Level 3) of the Borger CGU was determined using FVLCOD. The FVLCOD was calculated based on discounted after-tax cash flows using forward prices and cost estimates. Key assumptions in the determination of future cash flows included forward crude oil prices, forward crack spreads, future capital expenditures, operating costs, terminal values and the discount rate. Forward crack spreads were based on quoted near-month contracts for WTI and spot prices for gasoline and diesel. Crude Oil and Forward Crack Spreads Forward prices are based on Management’s best estimate and corroborated with third-party data. As at September 30, 2020, the forward prices used to determine future cash flows were: • WTI forward prices used for 2021 to 2022 ranged from US$36.36 per barrel to US$50.84 per barrel and 2023 to 2025 ranged from US$49.66 per barrel to US$58.74 per barrel. • WTI to West Texas Sour differential used for 2021 to 2022 ranged from US$0.37 per barrel to US$1.73 per barrel and 2023 to 2025 ranged from US$1.21 per barrel to US$1.81 per barrel. • Group 3 forward market crack spread used for 2021 to 2022 ranged from US$11.56 per barrel to US$13.23 per barrel and 2023 to 2025 ranged from US$11.79 per barrel to US$16.58 per barrel. • Subsequent prices were extrapolated using a two percent growth rate to determine future cash flows up to year 2035. Discount Rates Discounted future cash flows were determined by applying a discount rate of 10 percent based on the individual characteristics of the CGU, and other economic and operating factors. Sensitivities The sensitivity analysis below shows the impact that a change in the discount rate or forward commodity prices would have had on the calculated recoverable amount in the impairment testing completed as at September 30, 2020 for the following CGU: Increase (Decrease) to Recoverable Amount One Percent Increase in the Discount Rate One Percent Decrease in the Discount Rate Five Percent Increase in the Forward Price Estimates Five Percent Decrease in the Forward Price Estimates Borger (71 ) 81 263 (264 ) 2020 ROU Asset Impairments As at March 31, 2020, the temporary suspension of the Company’s crude-by-rail program was considered to be an indicator of impairment for the railcar CGU. As a result, the CGU was tested for impairment and an impairment expense of $3 2019 Upstream Impairments As at December 31, 2019, the Company tested its Conventional CGUs for impairment as there were indicators of impairment due to a decline in forward natural gas prices. As at December 31, 2019, there were no impairments of goodwill or the Company’s CGUs. 2018 Net Upstream Impairments As at December 31, 2018, the Company tested its upstream CGUs for impairment. As at December 31, 2018, there was no impairment of goodwill or the Company’s CGUs. However, the impairment test provided evidence that previously recognized impairment losses should be reversed. As at December 31, 2018, the recoverable amount of the Clearwater CGU was estimated to be $761 million. Earlier in 2018 and 2017, impairment losses of $100 million and $56 million, respectively, were recorded due to a decline in forward prices. The impairment was recorded as additional DD&A in the Conventional segment (formerly Deep Basin). In the fourth quarter of 2018, the Company reversed $132 million of impairment losses, net of the DD&A that would have been recorded had no impairments been recorded. The reversal was due to improved recovery, extensions and well performance and changes to the development plan. B) Asset Impairments and Write-downs Exploration and Evaluation Assets For the year ended December 31, 2020 , $9 million and $82 million of previously capitalized E&E costs were written off in the Oil Sands segment and Conventional segment, respectively carrying value was not considered to be recoverable and recorded as exploration expense. In 2019, $18 million and $64 million of previously capitalized E&E costs were written off in the Oil Sands segment and Conventional segment, respectively, as the carrying value was not considered to be recoverable and recorded as exploration expense. In 2018, Management completed a comprehensive review of the Conventional development plan, formerly known as Deep Basin, considering factors such as well inventory, pace of development, infrastructure constraints, economic thresholds and limited capital spending on the assets going forward. As such, previously capitalized E&E costs of $2.1 billion were written off as exploration expense in the Elmworth, Wapiti, Kaybob, Edson and Clearwater areas within the Conventional segment Property, Plant and Equipment, Net For the year ended December 31, 2020, $ 48 costs relating to information technology assets were written off due to synergies identified as a result of the Arrangement. The impairment was recorded as additional DD&A in the Corporate and Eliminations segment.

Discontinued Operations

Discontinued Operations	12 Months Ended
	Dec. 31, 2020
Disclosure Of Discontinued Operations [Abstract]
Discontinued Operations	11. DISCONTINUED OPERATIONS The results of operations from the former Conventional segment was reported as a discontinued operation. For the year ended December 31, 2018, the Company recorded net earnings from discontinued operations of $247 million. The cash flows from discontinued operations reported in the Consolidated Statement of Cash Flows were $36 million related to cash from operating activities and $404 million related to cash from investing activities. On January 5, 2018, the Company completed the sale of its Suffield crude oil and natural gas operations in southern Alberta for cash proceeds of $512 million, before closing adjustments. A before-tax gain on discontinuance of $343 million was recorded on the sale.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2020
Disclosure Of Income Tax Expense Continuing Operations [Abstract]
Income Taxes	12. INCOME TAXES The provision for income taxes is: For the years ended December 31, 2020 2019 2018 Current Tax Canada (14 ) 14 (128 ) United States 1 3 2 Total Current Tax Expense (Recovery) (13 ) 17 (126 ) Deferred Tax Expense (Recovery) (838 ) (814 ) (884 ) Tax Expense (Recovery) From Continuing Operations (851 ) (797 ) (1,010 ) For the year ended December 31, 2020, a deferred tax recovery was recorded due to an impairment of the Borger CGU, impairment in the Conventional segment and current period operating losses that will be carried forward, excluding unrealized foreign exchange gains and losses on long-term debt. In 2020, the Government of Alberta accelerated the reduction in the provincial corporate tax rate from 12 percent to eight percent. In 2019, the Government of Alberta enacted a reduction in the provincial corporate tax rate from 12 percent to eight percent over four years. As a result, the Company recorded a deferred income tax recovery of $671 million for the year ended December 31, 2019. In addition, the Company recorded a deferred income tax recovery of $387 million due to an internal restructuring of the Company’s U.S. operations resulting in a step-up in the tax basis of the Company’s refining assets. In 2018, the Company recorded a deferred tax recovery related to current period losses, including the write-down of the Conventional E&E assets and a $78 million recovery arising from an adjustment to the tax basis of the Company’s refining assets. The increase in tax basis was a result of the Company’s partner recognizing a taxable gain on its interest in WRB, which due to an election filed with the U.S. tax authorities, was added to the tax basis of WRB’s assets. The maximum recovery related to the carry back of losses to recover tax paid was reached in 2018. The following table reconciles income taxes calculated at the Canadian statutory rate with the recorded income taxes: For the years ended December 31, 2020 2019 2018 Earnings (Loss) From Continuing Operations Before Income Tax (3,230 ) 1,397 (3,926 ) Canadian Statutory Rate 24.0% 26.5% 27.0% Expected Income Tax Expense (Recovery) From Continuing Operations (775 ) 370 (1,060 ) Effect on Taxes Resulting From: Statutory and Other Rate Differences 19 (52 ) (57 ) Non-Taxable Capital (Gains) Losses (42 ) (38 ) 89 Non-Recognition of Capital (Gains) Losses (42 ) (39 ) 87 Adjustments Arising From Prior Year Tax Filings (8 ) 4 3 Recognition of U.S. Tax Basis - (387 ) (78 ) Alberta Corporate Rate Reduction (7 ) (671 ) - Other 4 16 6 Total Tax Expense (Recovery) From Continuing Operations (851 ) (797 ) (1,010 ) Effective Tax Rate 26.3% (57.1)% 25.7% The analysis of deferred income tax liabilities and deferred income tax assets is as follows: For the years ended December 31, 2020 2019 Deferred Income Tax Liabilities Deferred Income Tax Liabilities to be Settled Within Twelve Months - 3 Deferred Income Tax Liabilities to be Settled After More Than Twelve Months 4,146 4,540 4,146 4,543 Deferred Income Tax Assets Deferred Income Tax Assets to be Recovered Within Twelve Months (88 ) (113 ) Deferred Income Tax Assets to be Recovered After More Than Twelve Months (860 ) (398 ) (948 ) (511 ) Net Deferred Income Tax Liability 3,198 4,032 The deferred income tax assets and liabilities to be settled within twelve months represents Management’s estimate of the timing of the reversal of temporary differences and may not correlate to the current income tax expense of the subsequent year. The movement in deferred income tax liabilities and assets, without taking into consideration the offsetting of balances within the same tax jurisdiction, is: Deferred Income Tax Liabilities PP&E Risk Management Other Total As at December 31, 2018 5,450 44 51 5,545 Charged (Credited) to Earnings (927 ) (43 ) (7 ) (977 ) Charged (Credited) to OCI (25 ) - - (25 ) As at December 31, 2019 4,498 1 44 4,543 Charged (Credited) to Earnings (367 ) (1 ) (22 ) (390 ) Charged (Credited) to OCI (7 ) - - (7 ) As at December 31, 2020 4,124 - 22 4,146 Deferred Income Tax Assets Unused Tax Losses Risk Management Other Total As at December 31, 2018 (357 ) (1 ) (326 ) (684 ) Charged (Credited) to Earnings 129 - 34 163 Charged (Credited) to OCI 3 - 7 10 As at December 31, 2019 (225 ) (1 ) (285 ) (511 ) Charged (Credited) to Earnings (448 ) (12 ) 12 (448 ) Charged (Credited) to OCI 14 - (3 ) 11 As at December 31, 2020 (659 ) (13 ) (276 ) (948 ) Net Deferred Income Tax Liabilities Total Net Deferred Income Tax Liabilities as at December 31, 2018 4,861 Charged (Credited) to Earnings (814 ) Charged (Credited) to OCI (15 ) Net Deferred Income Tax Liabilities as at December 31, 2019 4,032 Charged (Credited) to Earnings (838 ) Charged (Credited) to OCI 4 Net Deferred Income Tax Liabilities as at December 31, 2020 3,198 The deferred income tax asset of $36 million (2019 – $nil) represents net deductible temporary differences in the U.S. jurisdiction which has been fully recognized, as the probability of realization is expected due to a forecasted taxable income. No The approximate amounts of tax pools available, including tax losses, are: As at December 31, 2020 2019 Canada 6,540 6,113 United States 3,117 2,648 9,657 8,761 As at December 31, 2020, the above tax pools included $ 1,682 1,084 . Also included in the December 31, 2020 tax pools are Canadian net capital losses totaling $ 85 22 254

Per Share Amounts

Per Share Amounts	12 Months Ended
	Dec. 31, 2020
Earnings Per Share [Abstract]
Per Share Amounts	13. PER SHARE AMOUNTS A) Net Earnings (Loss) Per Share – Basic and Diluted For the years ended December 31, 2020 2019 2018 Earnings (Loss) From: Continuing Operations (2,379 ) 2,194 (2,916 ) Discontinued Operations - - 247 Net Earnings (Loss) (2,379 ) 2,194 (2,669 ) Basic – Weighted Average Number of Shares 1,228.9 1,228.8 1,228.8 Dilutive Effect of Cenovus Net Settlement Rights - 0.6 0.4 Diluted – Weighted Average Number of Shares 1,228.9 1,229.4 1,229.2 Basic and Diluted Earnings (Loss) Per Share From: ($) Continuing Operations (1.94 ) 1.78 (2.37 ) Discontinued Operations - - 0.20 (1.94 ) 1.78 (2.17 ) As at December 31, 2020, 31 B) Common Share Dividend The Company temporarily suspended its common share dividend in response to the low global oil price environment. Prior to the suspension, the Company paid common share dividends of $77 million or $0.0625 ). The declaration of dividends is at the sole discretion of the Company’s Board of Directors and is considered quarterly. The Company’s Board of Directors declared a first quarter dividend of $0.0175 per common share, payable on March 31, 2021, to common shareholders of record as of March 15, 2021. C) Preferred Share Dividend Subsequent to the closing of the Arrangement on January 1, 2021, the outstanding Husky preferred shares were exchanged for Cenovus preferred shares (see Note 39). The Company’s Board of Directors declared first quarter dividends for its Cenovus series 1, 2, 3, 5, and 7 first preferred shares, payable on March 31, 2021, in the amount of $8 million

Cash and Cash Equivalents

Cash and Cash Equivalents	12 Months Ended
	Dec. 31, 2020
Cash And Cash Equivalents [Abstract]
Cash and Cash Equivalents	14. CASH AND CASH EQUIVALENTS As at December 31, 2020 2019 Cash 368 108 Short-Term Investments 10 78 378 186

Accounts Receivable and Accrued

Accounts Receivable and Accrued Revenues	12 Months Ended
	Dec. 31, 2020
Trade And Other Current Receivables [Abstract]
Accounts Receivable and Accrued Revenues	15. ACCOUNTS RECEIVABLE AND ACCRUED REVENUES As at December 31, 2020 2019 Accruals 1,053 1,221 Prepaids and Deposits 121 54 Partner Advances 175 16 Trade 96 212 Joint Operations Receivables 35 36 Other 8 17 1,488 1,556

Inventories

Inventories	12 Months Ended
	Dec. 31, 2020
Classes Of Inventories [Abstract]
Inventories	16. INVENTORIES As at December 31, 2020 2019 Product Refining and Marketing 613 874 Oil Sands 382 570 Conventional 1 1 Parts and Supplies 93 87 1,089 1,532 During the year ended December 31, 2020, approximately $ 9,996 As at March 31, 2020, the Company recorded $588 million in non-cash inventory write-downs of its crude oil blend, condensate and refined product inventory. Subsequently, $ 547 39 As at December 31, 2019, the Company recorded a $25 million write-down in refined product inventory. The inventory write-down was realized in 2020.

Exploration and Evaluation Asse

Exploration and Evaluation Assets	12 Months Ended
	Dec. 31, 2020
Disclosure Of Exploration And Evaluation Assets [Abstract]
Exploration and Evaluation Assets	17. EXPLORATION AND EVALUATION ASSETS Total As at December 31, 2018 785 Additions 73 Exploration Expense (Note 10) (82 ) Change in Decommissioning Liabilities 9 Exchange Rate Movements and Other 2 As at December 31, 2019 787 Additions 48 Transfers to PP&E (Note 18) (1) (47 ) Exploration Expense (Note 10) (91 ) Depletion (18 ) Change in Decommissioning Liabilities 5 Divestitures (Note 8) (61 ) As at December 31, 2020 623 (1) Includes the $41 million reclassification of the GORR retained in the sale of the Marten Hills assets (see Note 8).

Property, Plant and Equipment,

Property, Plant and Equipment, Net	12 Months Ended
	Dec. 31, 2020
Disclosure Of Property Plant And Equipment [Abstract]
Property, Plant and Equipment, Net	18. PROPERTY, PLANT AND EQUIPMENT, NET Upstream Assets Development & Production Other Upstream Refining Equipment Other (1) Total COST As at December 31, 2018 28,046 333 5,632 1,213 35,224 Adjustment for Change in Accounting Policy (2) - - (4 ) - (4 ) Additions 695 - 228 193 1,116 Change in Decommissioning Liabilities 340 - 9 5 354 Exchange Rate Movements and Other (9 ) - (288 ) 3 (294 ) Divestitures (Note 8) (40 ) - - - (40 ) As at December 31, 2019 29,032 333 5,577 1,414 36,356 Additions 475 - 243 93 811 Transfers From E&E Assets (Note 17) 6 41 - - 47 Change in Decommissioning Liabilities (11 ) - 3 2 (6 ) Exchange Rate Movements and Other (6 ) - (152 ) (1 ) (159 ) Divestitures (3 ) - - - (3 ) As at December 31, 2020 29,493 374 5,671 1,508 37,046 ACCUMULATED DEPRECIATION, DEPLETION AND AMORTIZATION As at December 31, 2018 3,918 333 1,442 833 6,526 Adjustment for Change in Accounting Policy (2) - - (1 ) - (1 ) Depreciation, Depletion and Amortization 1,735 - 241 75 2,051 Impairment Charges (Note 10) 20 - - 10 30 Exchange Rate Movements and Other 31 - (86 ) - (55 ) Divestitures (Note 8) (29 ) - - - (29 ) As at December 31, 2019 5,675 333 1,596 918 8,522 Depreciation, Depletion and Amortization 1,768 - 242 109 2,119 Impairment Charges (Note 10) 607 - 450 52 1,109 Exchange Rate Movements and Other (22 ) - (93 ) - (115 ) As at December 31, 2020 8,028 333 2,195 1,079 11,635 CARRYING VALUE As at December 31, 2018 24,128 - 4,190 380 28,698 As at December 31, 2019 23,357 - 3,981 496 27,834 As at December 31, 2020 21,465 41 3,476 429 25,411 (1) Primarily consists of crude-by-rail terminal, office furniture, fixtures, leasehold improvements, information technology and aircraft. (2) Effective January 1, 2019, the Company adopted IFRS 16. PP&E includes the following amounts in respect of assets under construction and not subject to DD&A: As at December 31, 2020 2019 Development and Production 1,807 1,836 Refining Equipment 226 172 2,033 2,008

Right of Use Assets, Net

Right of Use Assets, Net	12 Months Ended
	Dec. 31, 2020
Disclosure Of Quantitative Information About Rightofuse Assets [Abstract]
Right of Use Assets, Net	19. RIGHT-OF-USE ASSETS, NET Real Estate Railcars & Barges Storage Assets (1) Refining Equipment Other Total COST As at January 1, 2019 (2) 517 63 292 13 9 894 Additions 10 436 172 - 6 624 Terminations - - (11 ) - - (11 ) Reclassifications (8 ) - - - - (8 ) Re-measurement - (2 ) 18 (2 ) - 14 Exchange Rate Movements and Other (10 ) (2 ) (7 ) (1 ) (1 ) (21 ) As at December 31, 2019 509 495 464 10 14 1,492 Additions 1 18 22 5 7 53 Terminations - - (1 ) - - (1 ) Modifications - - 1 - (3 ) (2 ) Reclassifications (14 ) - - - - (14 ) Re-measurement - (20 ) 19 - (1 ) (2 ) Exchange Rate Movements and Other (1 ) (13 ) (8 ) - (2 ) (24 ) As at December 31, 2020 495 480 497 15 15 1,502 ACCUMULATED DEPRECIATION As at January 1, 2019 (2) - - - 1 - 1 Depreciation 29 55 75 2 4 165 Impairment Charges (Note 10) 3 - - - - 3 Terminations - - (1 ) - - (1 ) Exchange Rate Movements and Other - - (1 ) - - (1 ) As at December 31, 2019 32 55 73 3 4 167 Depreciation 27 86 95 2 5 215 Impairment Charges (Note 10) - 3 - - - 3 Terminations - - (1 ) - - (1 ) Exchange Rate Movements and Other (1 ) (13 ) (5 ) - (2 ) (21 ) As at December 31, 2020 58 131 162 5 7 363 CARRYING VALUE As at January 1, 2019 (2) 517 63 292 12 9 893 As at December 31, 2019 477 440 391 7 10 1,325 As at December 31, 2020 437 349 335 10 8 1,139 (1) Includes caverns and tanks. (2) Effective January 1, 2019, the Company adopted IFRS 16.

Other Assets

Other Assets	12 Months Ended
	Dec. 31, 2020
Other Noncurrent Assets [Abstract]
Other Assets	20. OTHER ASSETS As at December 31, 2020 2019 Intangible Assets 89 101 Equity Investments (Note 35A) 52 52 Investment in Associate (Note 8) 97 - Net Investment in Finance Leases 52 30 Long-Term Receivables and Prepaids 11 28 Other 12 - 313 211 In 2019, Cenovus entered into an agreement to assume a firm capacity shipper position in a pipeline transportation services agreement from a third party. The fee was recorded as an intangible asset at cost and will be amortized over the life of the contract of approximately 10 years.

Goodwill

Goodwill	12 Months Ended
	Dec. 31, 2020
Goodwill [Abstract]
Goodwill	21. GOODWILL As at December 31, 2020 and 2019, the carrying amount of goodwill associated with the Company’s Primrose (Foster Creek) CGU and Christina Lake CGU was $1,171 million and $1,101 million For the purposes of impairment testing, goodwill is allocated to the CGU to which it relates. The assumptions used to test Cenovus’s goodwill for impairment as at December 31, 2020 are consistent to those disclosed in Note 10. There was no impairment of goodwill as at December 31, 2020.

Accounts Payable and Accrued Li

Accounts Payable and Accrued Liabilities	12 Months Ended
	Dec. 31, 2020
Trade And Other Current Payables [Abstract]
Accounts Payable and Accrued Liabilities	22. ACCOUNTS PAYABLE AND ACCRUED LIABILITIES As at December 31, 2020 2019 Accruals 912 1,085 Trade 608 954 Interest 77 49 Partner Advances 175 16 Employee Long-Term Incentives 130 60 Joint Operations Payable 6 2 Risk Management 58 2 Onerous Contract Provisions 26 17 Other 26 44 2,018 2,229

Short-Term Borrowings

Short-Term Borrowings	12 Months Ended
	Dec. 31, 2020
Short Term Borrowings Disclosure [Abstract]
Short-Term Borrowings	23. SHORT-TERM BORROWINGS The Company has uncommitted demand facilities of $ 1.6 no 441 WRB has uncommitted demand facilities of US$300 million (the Company’s proportionate share – US$150 million) available to cover short-term working capital requirements. As at December 31, 2020, US$ 190 95 121

Long-term Debt and Capital Stru

Long-term Debt and Capital Structure	12 Months Ended
	Dec. 31, 2020
Borrowings [Abstract]
Long-term Debt and Capital Structure	24. LONG-TERM DEBT AND CAPITAL STRUCTURE As at December 31, Notes 2020 2019 Revolving Term Debt (1) A - 265 U.S. Dollar Denominated Unsecured Notes B 7,510 6,492 Total Debt Principal 7,510 6,757 Debt Discounts and Transaction Costs (69 ) (58 ) Long-Term Debt 7,441 6,699 (1) Revolving term debt may include Bankers’ Acceptances, London Interbank Offered Rate based loans, prime rate loans and U.S. base rate loans. The weighted average interest rate on outstanding debt, including the Company’s proportionate share of the WRB uncommitted demand facilities, for the year ended December 31, 2020 was 4.9 As at December 31, 2020, the Company is in compliance with all of the terms of its debt agreements. A) Committed Credit Facilities Cenovus has in place a committed revolving credit facility that consists of a $1.2 billion tranche and a $3.3 billion tranche with maturity dates of November 30, 2022 and November 30, 2023, respectively. In April 2020, the Company added a committed credit facility with capacity of $1.1 billion to further support the Company’s financial resilience in the current market environment. On December 31, 2020, the Company cancelled the $1.1 billion credit facility. B) U.S. Dollar Denominated Unsecured Notes The remaining principal amounts of the Company’s U.S. dollar denominated unsecured notes are: 2020 2019 As at December 31, US$ Principal Amount Total C$ Equivalent US$ Principal Amount Total C$ Equivalent 3.00% due August 15, 2022 500 637 500 650 3.80% due September 15, 2023 450 573 450 585 5.38% due July 15, 2025 1,000 1,273 - - 4.25% due April 15, 2027 962 1,225 962 1,249 5.25% due June 15, 2037 583 742 641 833 6.75% due November 15, 2039 1,390 1,770 1,400 1,818 4.45% due September 15, 2042 155 198 155 202 5.20% due September 15, 2043 58 74 58 75 5.40% due June 15, 2047 800 1,018 832 1,080 5,898 7,510 4,998 6,492 The Company has in place a base shelf prospectus that allows the Company to offer, from time to time, up to US$5.0 billion, or the equivalent in other currencies, of debt securities, common shares, preferred shares, subscription receipts, warrants, share purchase contracts and units in Canada, the U.S. and elsewhere where permitted by law. The base shelf prospectus will expire in October 2021. Offerings under the base shelf prospectus are subject to market conditions. On July 30, 2020, Cenovus completed a public offering in the U.S., under the Company’s U.S. base shelf prospectus, of senior unsecured notes in the aggregate principal of US$1.0 billion due in 2025. As at December 31, 2020, US $3.7 In addition, during the year ended December 31, 2020, the Company paid US$81 million to repurchase a portion of its unsecured notes with a principal amount of US$100 million. A gain on the repurchase of $25 million was recorded in finance costs (see Note 6). C) Mandatory Debt Payments As at December 31, 2020 US$ Principal Amount Total C$ Equivalent 2022 500 637 2023 450 573 2025 1,000 1,273 Thereafter 3,948 5,027 5,898 7,510 D) Capital Structure Cenovus’s capital structure objectives remain unchanged from previous periods. Cenovus’s capital structure consists of shareholders’ equity plus Net Debt. Net Debt includes the Company’s short-term borrowings, and the current and long-term portions of long-term debt, net of cash and cash equivalents and short-term investments. Cenovus conducts its business and makes decisions consistent with that of an investment grade company. The Company’s objectives when managing its capital structure are to maintain financial flexibility, preserve access to capital markets, ensure its ability to finance internally generated growth and to fund potential acquisitions while maintaining the ability to meet the Company’s financial obligations as they come due. To ensure financial resilience, Cenovus may, among other actions, adjust capital and operating spending, draw down on its credit facilities or repay existing debt, adjust dividends paid to shareholders, repurchase the Company’s common shares for cancellation, issue new debt, or issue new shares. Cenovus monitors its capital structure and financing requirements using, among other things, non-GAAP financial metrics consisting of Net Debt to Adjusted Earnings Before Interest, Taxes and DD&A (“Adjusted EBITDA”) and Net Debt to Capitalization. These metrics are used to steward Cenovus’s overall debt position as measures of Cenovus’s overall financial strength. Cenovus targets a Net Debt to Adjusted EBITDA ratio of less than 2.0 times over the long-term. This ratio may periodically be above the target due to factors such as persistently low commodity prices. Net Debt to Adjusted EBITDA (1) As at December 31, 2020 2019 2018 Short-Term Borrowings 121 - - Current Portion of Long-Term Debt - - 682 Long-Term Debt 7,441 6,699 8,482 Less: Cash and Cash Equivalents (378 ) (186 ) (781 ) Net Debt 7,184 6,513 8,383 Net Earnings (Loss) (2,379 ) 2,194 (2,669 ) Add (Deduct): Finance Costs 536 511 628 Interest Income (9 ) (12 ) (19 ) Income Tax Expense (Recovery) (851 ) (797 ) (920 ) Depreciation, Depletion and Amortization 3,464 2,249 2,131 Exploration Expense 91 82 2,123 Unrealized (Gain) Loss on Risk Management 56 149 (1,249 ) Foreign Exchange (Gain) Loss, Net (181 ) (404 ) 854 Re-measurement of Contingent Payment (80 ) 164 50 (Gain) Loss on Discontinuance - - (301 ) (Gain) Loss on Divestitures of Assets (81 ) (2 ) 795 Other (Income) Loss, Net 40 9 13 Adjusted EBITDA 606 4,143 1,436 Net Debt to Adjusted EBITDA 11.9x 1.6x 5.8x (1) IFRS 16 was adopted January 1, 2019 using the modified retrospective approach; therefore, comparative information has not been restated. Net Debt to Capitalization As at December 31, 2020 2019 2018 Net Debt 7,184 6,513 8,383 Shareholders’ Equity 16,707 19,201 17,468 23,891 25,714 25,851 Net Debt to Capitalization 30% 25% 32% Cenovus also manages its Net Debt to Capitalization ratio to ensure compliance with the associated covenant as defined in its committed credit facility agreements. Under the terms of Cenovus’s committed credit facility, the Company is required to maintain a debt to capitalization ratio, as defined in the agreements, not to exceed 65 percent. The Company is well below this limit.

Lease Liabilities

Lease Liabilities	12 Months Ended
	Dec. 31, 2020
Lease Liabilities [Abstract]
Lease Liabilities	25. LEASE LIABILITIES 2020 2019 Lease Liabilities, Beginning of Year 1,916 1,494 Additions 49 590 Interest Expense (Note 6) 87 82 Lease Payments (284 ) (232 ) Terminations (1 ) (11 ) Modifications (2 ) - Re-measurement (2 ) 15 Exchange Rate Movements and Other (6 ) (22 ) Lease Liabilities, End of Year 1,757 1,916 Less: Current Portion 184 196 Long-Term Portion 1,573 1,720 The Company has lease liabilities for contracts related to office space, railcars, barges, storage assets, drilling and service rigs, and other refining and field equipment. Lease terms are negotiated on an individual basis and contain a wide range of different terms and conditions. For the years ended December 31, 2020 2019 Variable Lease Payments 16 19 Short-Term Lease Payments 6 13 The Company has variable lease payments related to property taxes for real estate contracts. Short-term leases are leases with terms of twelve months or less. The Company has included extension options in the calculation of lease liabilities where the Company has the right to extend a lease term at its discretion and is reasonably certain to exercise the extension option. The Company does not have any significant termination options and the residual amounts are not material.

Contingent Payment

Contingent Payment	12 Months Ended
	Dec. 31, 2020
Disclosure Of Contingent Liabilities In Business Combination [Abstract]
Contingent Payment	26. CONTINGENT PAYMENT 2020 2019 Contingent Payment, Beginning of Year 143 132 Re-measurement (1) (80 ) 164 Liabilities Settled or Payable - (153 ) Contingent Payment, End of Year 63 143 Less: Current Portion 36 79 Long-Term Portion 27 64 (1) Contingent payment is carried at fair value. Changes in fair value are recorded in net earnings. In connection with the acquisition (the “Acquisition in 2017”) from ConocoPhillips Company and certain of its subsidiaries (collectively, “ConocoPhillips”), Cenovus agreed to make quarterly payments to ConocoPhillips during the five years subsequent to May 17, 2017 for quarters in which the average WCS crude oil price exceeds $52.00 per barrel during the quarter. The quarterly payment will be $6 million for each dollar that the WCS price exceeds $52.00 per barrel. The calculation includes an adjustment mechanism related to certain significant production outages at Foster Creek and Christina Lake, which may reduce the amount of a contingent payment. There are no maximum payment terms. The contingent payment is accounted for as a financial option. The fair value is estimated by calculating the present value of the future expected cash flows using an option pricing model, which assumes the probability distribution for WCS is based on the volatility of WTI options, volatility of Canadian-U.S. foreign exchange rate options and both WTI and WCS futures pricing, and discounted at a credit-adjusted risk-free rate. The contingent payment is re-measured at fair value at each reporting date with changes in fair value recognized in net earnings. As at December 31, 2020, no

Decommissioning Liabilities

Decommissioning Liabilities	12 Months Ended
	Dec. 31, 2020
Provision For Decommissioning Restoration And Rehabilitation Costs [Abstract]
Decommissioning Liabilities	27. DECOMMISSIONING LIABILITIES The decommissioning provision represents the present value of the expected future costs associated with the retirement of upstream crude oil and natural gas assets, refining facilities and the crude-by-rail terminal. The aggregate carrying amount of the obligation is: 2020 2019 Decommissioning Liabilities, Beginning of Year 1,235 875 Liabilities Incurred 14 3 Liabilities Settled (42 ) (52 ) Liabilities Disposed (2 ) (8 ) Change in Estimated Future Cash Flows 13 21 Change in Discount Rate (28 ) 339 Unwinding of Discount on Decommissioning Liabilities (Note 6) 57 58 Foreign Currency Translation 1 (1 ) Decommissioning Liabilities, End of Year 1,248 1,235 As at December 31, 2020, the undiscounted amount of estimated future cash flows required to settle the obligation is $4,953 million (2019 – $5,173 million), which has been discounted using a credit-adjusted risk-free rate of 5.0 two 40 Sensitivities Changes to the credit-adjusted risk-free rate or the inflation rate would have the following impact on the decommissioning liabilities: 2020 2019 As at December 31, Sensitivity Range Increase Decrease Increase Decrease Credit-Adjusted Risk-Free Rate ± one percent (228 ) 313 (236 ) 332 Inflation Rate ± one percent 321 (235 ) 340 (243 )

Other Liabilities

Other Liabilities	12 Months Ended
	Dec. 31, 2020
Disclosure Of Other Non Current Liabilities [Abstract]
Other Liabilities	28. OTHER LIABILITIES As at December 31, 2020 2019 Employee Long-Term Incentives 33 103 Pension and Other Post-Employment Benefit Plan (Note 29) 91 73 Onerous Contract Provisions 39 46 Other 18 19 181 241

Pensions and Other Post-Employm

Pensions and Other Post-Employment Benefits	12 Months Ended
	Dec. 31, 2020
Pensions And Other Post Employment Benefits [Abstract]
Pensions and Other Post-Employment Benefits	29. PENSIONS AND OTHER POST-EMPLOYMENT BENEFITS The Company provides employees with a pension that includes either a defined contribution or defined benefit component and other post-employment benefit plan. Most of the employees participate in the defined contribution pension. Employees who meet certain criteria may elect to move from the current defined contribution component to a defined benefit component for their future service. The defined benefit pension provides pension benefits at retirement based on years of service and final average earnings. Future enrollment is limited to eligible employees who meet certain criteria. The Company’s OPEB provides certain retired employees with health care and dental benefits until age 65 and life insurance benefits. The Company is required to file an actuarial valuation of its registered defined benefit pension with the provincial regulator at least every three years. The most recently filed valuation was dated December 31, 2019 and the next required actuarial valuation will be as at December 31, 2022. A) Defined Benefit and OPEB Plan Obligation and Funded Status Information related to defined benefit pension and OPEB plans, based on actuarial estimations, is: Pension Benefits OPEB As at December 31, 2020 2019 2020 2019 Defined Benefit Obligation Defined Benefit Obligation, Beginning of Year 158 167 22 21 Current Service Costs 13 11 1 1 Interest Costs (1) 5 6 - 1 Benefits Paid (6 ) (36 ) (2 ) (2 ) Plan Participant Contributions 2 2 - - Re-measurements: (Gains) Losses From Experience Adjustments 1 (4 ) (2 ) - (Gains) Losses From Changes in Financial Assumptions 15 12 1 1 Defined Benefit Obligation, End of Year 188 158 20 22 Plan Assets Fair Value of Plan Assets, Beginning of Year 107 113 - - Employer Contributions 6 9 - - Plan Participant Contributions 2 2 - - Benefits Paid (5 ) (35 ) - - Interest Income (1) 2 3 - - Re-measurements: Return on Plan Assets (Excluding Interest Income) 5 15 - - Fair Value of Plan Assets, End of Year 117 107 - - Pension and OPEB (Liability) (2) (71 ) (51 ) (20 ) (22 ) (1) Based on the discount rate of the defined benefit obligation at the beginning of the year. (2) Pension and OPEB liabilities are included in other liabilities on the Consolidated Balance Sheets. The weighted average duration of the defined benefit pension and OPEB obligations are 17.4 13.3 years B) Pension and OPEB Costs Pension Benefits OPEB For the years ended December 31, 2020 2019 2018 2020 2019 2018 Defined Benefit Plan Cost Current Service Costs 13 11 13 1 1 1 Past Service Costs – Curtailments - - (2 ) - - - Net Interest Costs 3 3 3 - 1 1 Re-measurements: Return on Plan Assets (Excluding Interest Income) (5 ) (15 ) 7 - - - (Gains) Losses From Experience Adjustments 1 (4 ) - (2 ) - - (Gains) Losses From Changes in Financial Assumptions 15 12 - 1 1 (1 ) Defined Benefit Plan Cost (Recovery) 27 7 21 - 3 1 Defined Contribution Plan Cost 22 21 22 - - - Total Plan Cost 49 28 43 - 3 1 C) Investment Objectives and Fair Value of Plan Assets The objective of the asset allocation is to manage the funded status of the plan at an appropriate level of risk, giving consideration to the security of the assets and the potential volatility of market returns and the resulting effect on both contribution requirements and pension expense. The long-term return is expected to achieve or exceed the return from a composite benchmark comprised of passive investments in appropriate market indices. The asset allocation structure is subject to diversification requirements and constraints which reduce risk by limiting exposure to individual equity investment and credit rating categories. The allocation of assets between the various types of investment funds is monitored regularly and is re-balanced monthly, if necessary. The asset allocation structure targets an investment of 25 70 25 35 zero 15 zero 10 zero 10 zero 10 The Company does not use derivative instruments to manage the risks of its plan assets. There has been no change in the process used by the Company to manage these risks from prior periods. The fair value of the plan assets is: As at December 31, 2020 2019 Equity Funds 58 59 Fixed Income Funds 35 35 Real Estate Funds 6 - Listed Infrastructure Funds 8 9 Emerging Market Debt Funds 7 - Non-Invested Assets 1 2 Cash and Cash Equivalents 2 2 117 107 Fair value of the equity, fixed income and listed infrastructure assets are based on the trading price of the underlying funds (Level 1). The fair value of the real estate fund reflects the appraisal valuation for each property investment (Level 2). The fair value of the non-invested assets is the discounted value of the expected future payments (Level 3). The defined benefit plan does not hold any direct investment in Cenovus shares. D) Funding The defined benefit pension is funded in accordance with federal and provincial government pension legislation, where applicable. Contributions are made to trust funds administered by an independent trustee. The Company’s contributions to the defined benefit pension plan are based on the most recent actuarial valuation as at December 31, 2019, and direction of the Management Pension Committee and Human Resources and Compensation Committee of the Board of Directors. Employees participating in the defined benefit pension are required to contribute four percent of their pensionable earnings, up to an annual maximum, and the Company provides the balance of the funding necessary to ensure benefits will be fully provided for at retirement. The expected employer contributions for the year ended December 31, 2021 are $ 10 E) Actuarial Assumptions and Sensitivities Actuarial Assumptions The principal weighted average actuarial assumptions used to determine benefit obligations and expenses are as follows: Pension Benefits OPEB For the years ended December 31, 2020 2019 2018 2020 2019 2018 Discount Rate 2.50 % 3.00 % 3.50 % 2.50 % 3.00 % 3.50 % Future Salary Growth Rate 3.97 % 3.94 % 3.88 % 4.94 % 5.08 % 5.08 % Average Longevity (years) 88.3 88.2 88.2 88.2 88.2 88.1 Health Care Cost Trend Rate N/A N/A N/A 6.00 % 6.00 % 6.00 % The discount rates are determined with reference to market yields on high quality corporate debt instruments of similar duration to the benefit obligations at the end of the reporting period. Sensitivities The sensitivity of the defined benefit and OPEB obligation to changes in relevant actuarial assumptions is: 2020 2019 As at December 31, Increase Decrease Increase Decrease One Percent Change: Discount Rate (31 ) 40 (25 ) 32 Future Salary Growth Rate 4 (4 ) 3 (3 ) Health Care Cost Trend Rate 1 (1 ) 1 (1 ) One Year Change in Assumed Life Expectancy 4 (4 ) 3 (3 ) The sensitivity analysis is based on a change in an assumption while holding all other assumptions constant; however, the changes in some assumptions may be correlated. The same methodologies have been used to calculate the sensitivity of the defined benefit obligation to significant actuarial assumptions as have been applied when calculating the defined benefit pension liability recorded on the Consolidated Balance Sheets. F) Risks Through its defined benefit pension and OPEB plans, the Company is exposed to actuarial risks, such as longevity risk, interest rate risk, investment risk and salary risk. Longevity Risk The present value of the defined benefit plan obligation is calculated by reference to the best estimate of the mortality of plan participants both during and after their employment. An increase in the life expectancy of participants will increase the defined benefit plan obligation. Interest Rate Risk A decrease in corporate bond yields will increase the defined benefit plan obligation, although this will be partially offset by an increase in the return on debt holdings. Investment Risk The present value of the defined benefit plan obligation is calculated using a discount rate determined by reference to high quality corporate bond yields. If the return on plan assets is below this rate, a plan deficit will result. Due to the long-term nature of the plan liabilities, a higher portion of the plan assets are invested in equity securities than in debt instruments and real estate. Salary Risk The present value of the defined benefit plan obligation is calculated by reference to the future salaries of plan participants. As such, an increase in the salary of the plan participants will increase the defined benefit obligation.

Share Capital

Share Capital	12 Months Ended
	Dec. 31, 2020
Disclosure Of Share Capital Reserves And Other Equity Interest [Abstract]
Share Capital	30. SHARE CAPITAL A) Authorized Cenovus is authorized to issue an unlimited number of common shares and first and second preferred shares not exceeding, in aggregate, 20 percent of the number of issued and outstanding common shares. The first and second preferred shares may be issued in one or more series with rights and conditions to be determined by the Company’s Board of Directors prior to issuance and subject to the Company’s articles. Prior to the close of the Arrangement, Cenovus’s articles were amended effective December 30, 2020 to create the Cenovus series 1, 2, 3, 4, 5, 6, 7 and 8 first preferred shares. B) Issued and Outstanding 2020 2019 As at December 31, Number of Common Shares (thousands) Amount Number of Common Shares (thousands) Amount Outstanding, Beginning of Year 1,228,828 11,040 1,228,790 11,040 Common Shares Issued Under Stock Option Plan (Note 32) 42 - 38 - Outstanding, End of Year 1,228,870 11,040 1,228,828 11,040 There were no As at December 31, 2020, there were 27 Subsequent to December 31, 2020, the Company issued common shares and first preferred shares in connection to the Arrangement that closed on January 1, 2021 (see Note 39). C) Paid in Surplus Cenovus’s paid in surplus reflects the Company’s retained earnings prior to the split of Encana Corporation (“Encana”) under the plan of arrangement into two independent energy companies, Encana (now known as Ovintiv Inc.) and Cenovus (pre-arrangement earnings). In addition, paid in surplus includes stock-based compensation expense related to the Company’s NSRs discussed in Note 32A. Pre-Arrangement Earnings Stock-Based Compensation Total As at December 31, 2018 4,086 281 4,367 Stock-Based Compensation Expense - 10 10 As at December 31, 2019 4,086 291 4,377 Stock-Based Compensation Expense - 14 14 As at December 31, 2020 4,086 305 4,391

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income (Loss)	12 Months Ended
	Dec. 31, 2020
Disclosure Of Accumulated Other Comprehensive Income Loss [Abstract]
Accumulated Other Comprehensive Income (Loss)	31. ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) Defined Benefit Pension Plan Private Equity Instruments Foreign Currency Translation Adjustment Total As at December 31, 2018 (7 ) 15 1,030 1,038 Other Comprehensive Income (Loss), Before Tax 6 14 (228 ) (208 ) Income Tax (1 ) (2 ) - (3 ) As at December 31, 2019 (2 ) 27 802 827 Other Comprehensive Income (Loss), Before Tax (10 ) - (44 ) (54 ) Income Tax 2 - - 2 As at December 31, 2020 (10 ) 27 758 775

Stock-Based Compensation Plans

Stock-Based Compensation Plans	12 Months Ended
	Dec. 31, 2020
Disclosure Of Terms And Conditions Of Sharebased Payment Arrangement [Abstract]
Stock-Based Compensation Plans	32. STOCK-BASED COMPENSATION PLANS A) Employee Stock Option Plan Cenovus has an Employee Stock Option Plan that provides employees with the opportunity to exercise an option to purchase a common share of the Company. Option exercise prices approximate the market value for the common shares on the date the options were issued. Options granted are exercisable at 30 percent of the number granted after one year, an additional 30 percent of the number granted after two years and are fully exercisable after three years. Options expire after seven years. Options issued by the Company on or after February 24, 2011 have associated NSRs. The NSRs, in lieu of exercising the option, gives the option holder the right to receive the number of common shares that could be acquired with the excess value of the market price of Cenovus’s common shares at the time of exercise over the exercise price of the option. Alternatively, the holder may elect to exercise the option and receive a net cash payment equal to the excess of the market price received from the sale of the common shares over the exercise price of the option. The NSRs vest and expire under the same terms and conditions as the underlying options. Net Settlement Rights The weighted average unit fair value of NSRs granted during the year ended December 31, 2020 was $2.27 before considering forfeitures, which are considered in determining total cost for the period. The fair value of each NSR was estimated on its grant date using the Black-Scholes-Merton valuation model with weighted average assumptions as follows: Risk-Free Interest Rate 1.19 % Expected Dividend Yield 1.77 % Expected Volatility (1) 29.74 % Expected Life (years) 5.00 (1) Expected volatility has been based on historical share volatility of the Company and comparable industry peers. The following tables summarize information related to the NSRs: For the year ended December 31, 2020 Number of NSRs (thousands) Weighted Average Exercise Price ($) Outstanding, Beginning of Year 31,528 22.61 Granted 5,783 11.73 Exercised (42 ) 9.48 Forfeited (416 ) 23.52 Expired (6,256 ) 32.60 Outstanding, End of Year 30,597 18.52 Outstanding NSRs Exercisable NSRs As at December 31, 2020 Range of Exercise Price ($) Number of NSRs (thousands) Weighted Average Remaining Contractual Life (years) Weighted Average Exercise Price ($) Number of NSRs (thousands) Weighted Average Exercise Price ($) 5.00 to 9.99 2,796 4.2 9.48 1,596 9.48 10.00 to 14.99 12,921 5.2 12.27 4,189 13.53 15.00 to 19.99 2,691 2.3 19.47 2,691 19.47 20.00 to 24.99 3,078 1.1 22.26 3,078 22.26 25.00 to 29.99 8,540 0.1 28.37 8,540 28.37 30.00 to 34.99 571 0.5 32.27 571 32.27 30,597 2.9 18.52 20,665 21.94 The Arrangement on January 1, 2021 resulted in the accelerated vesting of outstanding NSRs held by non-executive employees and certain non-executive officers of the Company. In accordance with their terms, 2,738 thousand additional NSRs vested and were exercisable as a result of the accelerated vesting on January 1, 2021. B) Performance Share Units Cenovus has granted PSUs to certain employees under its Performance Share Unit Plan for Employees. PSUs are time-vested that entitle employees to receive, upon vesting, either a common share of Cenovus or a cash payment equal to the value of a Cenovus common share. The Company has recorded a liability of $ 65 nil The following table summarizes the information related to the PSUs held by Cenovus employees: For the year ended December 31, 2020 Number of PSUs (thousands) Outstanding, Beginning of Year 6,912 Granted 3,846 Vested and Paid Out (1,223 ) Cancelled (449 ) Units in Lieu of Dividends 198 Outstanding, End of Year 9,284 C) Restricted Share Units Cenovus has granted RSUs to certain employees under its Restricted Share Unit Plan for Employees. RSUs are whole-share units and entitle employees to receive, upon vesting, either a common share of Cenovus or a cash payment equal to the value of a Cenovus common share. RSUs generally vest after three years. RSUs are accounted for as liability instruments and are measured at fair value based on the market value of Cenovus’s common shares at each period end. The fair value is recognized as stock-based compensation costs over the vesting period. Fluctuations in the fair value are recognized as stock-based compensation costs in the period they occur. The Company has recorded a liability of $ 61 60 The following table summarizes the information related to the RSUs held by Cenovus employees: For the year ended December 31, 2020 Number of RSUs (thousands) Outstanding, Beginning of Year 8,372 Granted 2,686 Vested and Paid Out (2,606 ) Cancelled (234 ) Units in Lieu of Dividends 212 Outstanding, End of Year 8,430 D) Deferred Share Units Under two Deferred Share Unit Plans, Cenovus directors, officers and certain employees may receive DSUs, which are equivalent in value to a common share of the Company. Eligible employees have the option to convert either zero, 25 or 50 percent of their annual bonus award into DSUs. DSUs vest The Company has recorded a liability of $ 10 The following table summarizes the information related to the DSUs held by Cenovus directors, officers and employees: For the year ended December 31, 2020 Number of DSUs (thousands) Outstanding, Beginning of Year 1,237 Granted to Directors 288 Granted 30 Units in Lieu of Dividends 33 Redeemed (255 ) Outstanding, End of Year 1,333 E) Total Stock-Based Compensation For the years ended December 31, 2020 2019 2018 Net Settlement Rights 11 9 6 Performance Share Units 19 15 (6 ) Restricted Share Units 23 34 9 Deferred Share Units (4 ) 9 - Stock-Based Compensation Expense 49 67 9 Stock-Based Compensation Costs Capitalized 16 20 4 65 87 13

Employee Salaries and Benefit E

Employee Salaries and Benefit Expenses	12 Months Ended
	Dec. 31, 2020
Disclosure Of Salaries And Employee Benefits [Abstract]
Employee Salaries and Benefit Expenses	33. EMPLOYEE SALARIES AND BENEFIT EXPENSES For the years ended December 31, 2020 2019 2018 Salaries, Bonuses and Other Short-Term Employee Benefits 605 567 580 Post-Employment Benefits 33 29 30 Stock-Based Compensation Expense (Note 32) 49 67 9 Other Long-Term Incentive Benefits (4 ) 31 - Termination Benefits 9 6 63 692 700 682 Stock-based compensation includes the costs recorded during the year associated with NSRs, PSUs, RSUs and DSUs.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2020
Disclosure Of Transactions Between Related Parties [Abstract]
Related Party Transactions	34. RELATED PARTY TRANSACTIONS Key Management Compensation Key management includes Directors (executive and non-executive), Executive Officers, Senior Vice-Presidents and Vice-Presidents. The compensation paid or payable to key management is: For the years ended December 31, 2020 2019 2018 Salaries, Director Fees and Short-Term Benefits 21 24 20 Post-Employment Benefits 3 2 3 Stock-Based Compensation 15 22 5 Other Long-Term Incentive Benefits 1 1 - Termination Benefits 6 - 9 46 49 37 Post-employment benefits represent the present value of future pension benefits earned during the year.

Financial Instruments

Financial Instruments	12 Months Ended
	Dec. 31, 2020
Disclosure Of Financial Instruments [Abstract]
Financial Instruments	35. FINANCIAL INSTRUMENTS Cenovus’s financial assets and financial liabilities consist of cash and cash equivalents, accounts receivable and accrued revenues, net investment in finance leases, accounts payable and accrued liabilities, risk management assets and liabilities, investments in the equity of private companies, long-term receivables, lease liabilities, contingent payment, short-term borrowings and long-term debt. Risk management assets and liabilities arise from the use of derivative financial instruments. A) Fair Value of Non-Derivative Financial Instruments The fair values of cash and cash equivalents, accounts receivable and accrued revenues, accounts payable and accrued liabilities, and short-term borrowings approximate their carrying amount due to the short-term maturity of these instruments. The fair values of long-term receivables and net investment in finance leases approximate their carrying amounts due to the specific non-tradeable nature of these instruments. Long-term debt is carried at amortized cost. The estimated fair value of long-term debt has been determined based on the period-end trading prices on the secondary market (Level 2). As at December 31, 2020, the carrying value of Cenovus’s long-term debt was $7,441 million 8,608 Equity investments classified at FVOCI comprise equity investments in private companies. The Company classifies certain private equity instruments at FVOCI as they are not held for trading and fair value changes are not reflective of the Company’s operations. These assets are carried at fair value on the Consolidated Balance Sheets in other assets. Fair value is determined based on recent private placement transactions (Level 3) when available. The following table provides a reconciliation of changes in the fair value of private equity investments classified at FVOCI: 2020 2019 Fair Value, Beginning of Year 52 38 Change in Fair Value (1) - 14 Fair Value, End of Year 52 52 (1) Changes in fair value are recorded in OCI. B) Fair Value of Risk Management Assets and Liabilities The Company’s risk management assets and liabilities consist of crude oil swaps, futures, natural gas futures, and if entered into, crude oil options, condensate futures and swaps, foreign exchange swaps, interest rate swaps and cross currency interest rate swaps. Crude oil, condensate and, if entered into, natural gas contracts are recorded at their estimated fair value based on the difference between the contracted price and the period-end forward price for the same commodity, using quoted market prices or the period-end forward price for the same commodity extrapolated to the end of the term of the contract (Level 2). The fair value of foreign exchange swaps are calculated using external valuation models which incorporate observable market data, including foreign exchange forward curves (Level 2) and the fair value of interest rate swaps are calculated using external valuation models which incorporate observable market data, including interest rate yield curves (Level 2). The fair value of cross currency interest rate swaps are calculated using external valuation models which incorporate observable market data, including foreign exchange forward curves (Level 2) and interest rate yield curves (Level 2). Summary of Unrealized Risk Management Positions 2020 2019 Risk Management Risk Management As at December 31, Asset Liability Net Asset Liability Net Crude Oil, Natural Gas and Condensate 5 58 (53 ) 5 2 3 The following table presents the Company’s fair value hierarchy for risk management assets and liabilities carried at fair value: As at December 31, 2020 2019 Level 2 – Prices Sourced From Observable Data or Market Corroboration (53 ) 3 Prices sourced from observable data or market corroboration refers to the fair value of contracts valued in part using active quotes and in part using observable, market-corroborated data. The following table summarizes the changes in the fair value of Cenovus’s risk management assets and liabilities: 2020 2019 Fair Value of Contracts, Beginning of Year 3 160 Fair Value of Contracts Realized During the Year 252 7 Change in Fair Value of Contracts in Place at Beginning of Year and Contracts Entered Into During the Year (308 ) (156 ) Unrealized Foreign Exchange Gain (Loss) on U.S. Dollar Contracts - (8 ) Fair Value of Contracts, End of Year (53 ) 3 Financial assets and liabilities are offset only if Cenovus has the current legal right to offset and intends to settle on a net basis or settle the asset and liability simultaneously. Cenovus offsets risk management assets and liabilities when the counterparty, commodity, currency and timing of settlement are the same. No additional unrealized risk management positions are subject to an enforceable master netting arrangement or similar agreement that are not otherwise offset. The following table provides a summary of the Company’s offsetting risk management positions: 2020 2019 Risk Management Risk Management As at December 31, Asset Liability Net Asset Liability Net Recognized Risk Management Positions Gross Amount 70 123 (53 ) 13 10 3 Amount Offset (65 ) (65 ) - (8 ) (8 ) - Net Amount per Consolidated Financial Statements 5 58 (53 ) 5 2 3 The derivative liabilities do not have credit risk-related contingent features. Due to credit practices that limit transactions according to counterparties’ credit quality, the change in fair value through profit or loss attributable to changes in the credit risk of financial liabilities is immaterial. Cenovus pledges cash collateral with respect to certain of these risk management contracts, which is not offset against the related financial liability. The amount of cash collateral required will vary daily over the life of these risk management contracts as commodity prices change. Additional cash collateral is required if, on a net basis, risk management payables exceed risk management receivables on a particular day. As at December 31, 2020, $59 million was pledged as cash collateral (2019 – $nil). C) Fair Value of Contingent Payment The contingent payment is carried at fair value on the Consolidated Balance Sheets. Fair value is estimated by calculating the present value of the expected future cash flows using an option pricing model (Level 3), which assumes the probability distribution for WCS is based on the volatility of WTI options, volatility of Canadian to U.S. foreign exchange rate options and both WTI and WCS futures pricing, and discounted at a credit-adjusted risk-free rate of 2.0 percent. Fair value of the contingent payment has been calculated by Cenovus’s internal valuation team which consists of individuals who are knowledgeable and have experience in fair value techniques. As at December 31, 2020, the fair value of the contingent payment was estimated to be $63 million (2019 – $143 million). As at December 31, 2020, average WCS forward pricing for the remaining term of the contingent payment is $42.93 per barrel. The average implied volatility of WTI options and the Canadian to U.S. foreign exchange rate options used to value the contingent payment were 35.6 percent and 6.8 As at December 31, 2020 Sensitivity Range Increase Decrease WCS Forward Prices ± $5.00 per barrel (41 ) 32 WTI Option Volatility ± five percent (18 ) 17 Canadian to U.S. Dollar Foreign Exchange Rate Option Volatility ± five percent 7 (10 ) As at December 31, 2019 Sensitivity Range Increase Decrease WCS Forward Prices ± $5.00 per barrel (129 ) 80 WTI Option Volatility ± five percent (45 ) 42 Canadian to U.S. Dollar Foreign Exchange Rate Option Volatility ± five percent 10 (19 ) D) Earnings Impact of (Gains) Losses From Risk Management Positions For the years ended December 31, 2020 2019 2018 Realized (Gain) Loss (1) 252 7 1,554 Unrealized (Gain) Loss (2) 56 149 (1,249 ) (Gain) Loss on Risk Management From Continuing Operations 308 156 305 ( 1 ) Realized gains and losses on risk management are recorded in the reportable segment to which the derivative instrument relates. ( 2 ) Unrealized gains and losses on risk management are recorded in the Corporate and Eliminations segment.

Risk Management

Risk Management	12 Months Ended
	Dec. 31, 2020
Risk Management [Abstract]
Risk Management	36. RISK MANAGEMENT Cenovus is exposed to financial risks, including market risk related to commodity prices, foreign exchange rates, interest rates as well as credit risk and liquidity risk. To manage exposure to interest rate volatility, the Company may periodically enter into interest rate swap contracts. To mitigate the Company’s exposure to foreign exchange rate fluctuations, the Company periodically enters into foreign exchange contracts. To manage interest costs on short-term borrowings, the Company periodically enters into cross currency interest rate swaps. As at December 31, 2020, there were no To manage exposure to commodity price movements between when products are produced or purchased and when sold to the customer or used by Cenovus, the Company may periodically enter into financial positions as a part of ongoing operations to market the Company’s production and physical inventory positions of crude oil and condensate volumes. The Company has entered into risk management positions to help capture the incremental margin expected to be received in future periods at the time products will be sold. To mitigate overall exposure to the fluctuations in commodity prices, the Company may also enter into financial positions to protect the near-term and future cash flows. As at December 31, 2020, the fair value of financial positions was a net liability of $53 Net Fair Value of Risk Management Positions As at December 31, 2020 Notional Volumes (1) (2) Terms (3) Weighted Average Price (1) (2) Fair Value Asset (Liability) Crude Oil and Condensate Contracts WTI Fixed - Sell 19.6 MMbbls January 2021 - June 2022 US$43.99/bbl (113 ) WTI Fixed - Buy 11.7 MMbbls February 2021 - June 2022 US$44.55/bbl 59 Other Financial Positions (4) 1 Total Fair Value (53 ) (1) Million barrels (“MMbbls”). Barrel (“bbl”). (2) Notional volumes and weighted average price represent various contracts over the respective terms. The notional volumes and weighted average price may fluctuate from month to month as it represents the averages for various individual contracts with different terms. (3) Contract terms represents averages for various individual contracts with different terms and range from one to twenty-three months. (4) Other financial positions consist of risk management positions related to WCS and condensate differential contracts, Belvieu and natural gas fixed contracts and the Company’s Refining and Marketing segment. A) Commodity Price Risk Commodity price risk arises from the effect that fluctuations of forward commodity prices may have on the fair value or future cash flows of financial assets and liabilities. To partially mitigate exposure to commodity price risk, the Company has entered into various financial derivative instruments. The use of these derivative instruments is governed under formal policies and is subject to limits established by the Board of Directors. The Company’s policy does not allow the use of derivative instruments for speculative purposes. Crude Oil – The Company has used commodity futures and swaps, basis price risk management contracts, and costless collars to partially mitigate its exposure to the commodity price risk on its crude oil sales and to protect both near-term and future cash flows. Cenovus has entered into a number of transactions to help protect against widening light/heavy crude oil price differentials and to manage exposure to commodity price movements between when products are produced or purchased and when sold to the customer or used by Cenovus. In addition, the Company has entered into risk management positions to help mitigate the risk to incremental margin expected to be received in future periods at the time products will be sold. Condensate – The Company has used commodity futures and swaps, as well as basis price risk management contracts to partially mitigate its exposure to the commodity price risk on its condensate purchases. Natural Gas – The Company has used fixed price and basis instruments to partially mitigate its natural gas commodity price risk. Sensitivities The following table summarizes the sensitivity of the fair value of Cenovus’s risk management positions to independent fluctuations in commodity prices, with all other variables held constant. Management believes the fluctuations identified in the table below are a reasonable measure of volatility. The impact of fluctuating commodity prices on the Company’s open risk management positions could have resulted in unrealized gains (losses) impacting earnings before income tax as follows: As at December 31, 2020 Sensitivity Range Increase Decrease Crude Oil Commodity Price ± US$5.00 per bbl Applied to WTI and Condensate Hedges (44 ) 44 Crude Oil Differential Price ± US$2.50 per bbl Applied to Differential Hedges Tied to Production (2 ) 2 As at December 31, 2019 Sensitivity Range Increase Decrease Crude Oil Commodity Price ± US$5.00 per bbl Applied to WTI and Condensate Hedges 3 (3 ) Crude Oil Differential Price ± US$2.50 per bbl Applied to Differential Hedges Tied to Production 5 (5 ) B) Foreign Exchange Risk Foreign exchange risk arises from changes in foreign exchange rates that may affect the fair value or future cash flows of Cenovus’s financial assets or liabilities. As Cenovus operates in North America, fluctuations in the exchange rate between the U.S./Canadian dollar can have a significant effect on reported results. As disclosed in Note 7, Cenovus’s foreign exchange (gain) loss primarily includes unrealized foreign exchange gains and losses on the translation of the U.S. dollar debt issued from Canada. As at December 31, 2020, Cenovus had US$ 5,898 For the years ended December 31, 2020 2019 $0.05 Increase in the Canadian per U.S. Dollar Foreign Exchange Rate 300 250 $0.05 Decrease in the Canadian per U.S. Dollar Foreign Exchange Rate (300 ) (250 ) C) Interest Rate Risk Interest rate risk arises from changes in market interest rates that may affect earnings, cash flows and valuations. Cenovus has the flexibility to partially mitigate its exposure to interest rate changes by maintaining a mix of both fixed and floating rate debt. To manage exposure to interest rate volatility, the Company periodically enters into interest rate swap contracts. As at December 31, 2020, Cenovus had no interest rate swap contracts outstanding (2019 – $nil). To manage interest costs on short-term borrowings, the Company periodically enters into cross currency interest rate swaps. As at December 31, 2020, Cenovus had no As at December 31, 2020, the increase or decrease in net earnings for a one percent change in interest rates on floating rate debt amounts to $ 1 D) Credit Risk Credit risk arises from the potential that the Company may incur a financial loss if a counterparty to a financial instrument fails to meet its financial or performance obligations in accordance with agreed terms. Cenovus has in place a Credit Policy approved by the Audit Committee and the Board of Directors designed to ensure that its credit exposures are within an acceptable risk level as determined by the Company’s Enterprise Risk Management Policy. The Credit Policy outlines the roles and responsibilities related to credit risk, sets a framework for how credit exposures will be measured, monitored and mitigated, and sets parameters around credit concentration limits. Cenovus assesses the credit risk of new counterparties and continues risk-based monitoring of all counterparties on an ongoing basis. A substantial portion of Cenovus’s accounts receivable are with customers in the oil and gas industry and are subject to normal industry credit risks. Cenovus’s exposure to its counterparties is within credit policy tolerances. As at December 31, 2020, approximately 98 percent of the Company’s accruals, joint operations, trade receivables and net investment in finance leases were with investment grade counterparties (2019 – 97 percent), and as at December 31, 2020 and 2019, substantially all of the Company’s accounts receivable were outstanding less than 60 days. The average expected credit loss on the Company’s accruals, joint operations, trade receivables and net investment in finance leases was 0.5 percent as at December 31, 2020 (2019 – 0.3 percent). As at December 31, 2020, Cenovus had one counterparty (2019 – one counterparty) whose net settlement position individually accounted for more than 10 percent of the fair value of the Company’s accruals, joint operations, trade receivables and net investment in finance leases. E) Liquidity Risk Liquidity risk is the risk that the Company will not be able to meet all of its financial obligations as they become due. Liquidity risk also includes the risk of not being able to liquidate assets in a timely manner at a reasonable price. Cenovus manages its liquidity risk through the active management of cash and debt and by maintaining appropriate access to credit, which may be impacted by the Company’s credit ratings. As disclosed in Note 24, over the long term, Cenovus targets a Net Debt to Adjusted EBITDA of less than 2.0 times to manage the Company’s overall debt position. Cenovus manages its liquidity risk by ensuring that it has access to multiple sources of capital including: cash and cash equivalents, cash from operating activities, undrawn capacity on its committed credit facility and uncommitted demand facilities as well as availability under its base shelf prospectus. As at December 31, 2020, Cenovus had $ 378 4.5 $3.7 billion On January 1, 2021, with the close of the Arrangement, Cenovus obtained access to additional sources of capital (see Note 39). Undiscounted cash outflows relating to financial liabilities are: As at December 31, 2020 Less than 1 Year Years 2 and 3 Years 4 and 5 Thereafter Total Accounts Payable and Accrued Liabilities 2,018 - - - 2,018 Short-Term Borrowings (1) 121 - - - 121 Long-Term Debt (1) 385 1,965 1,966 8,627 12,943 Contingent Payment (2) 36 28 - - 64 Lease Liabilities (1) 254 445 365 1,412 2,476 As at December 31, 2019 Less than 1 Year Years 2 and 3 Years 4 and 5 Thereafter Total Accounts Payable and Accrued Liabilities 2,229 - - - 2,229 Long-Term Debt (1) 344 1,338 1,465 9,326 12,473 Contingent Payment (2) 79 69 - - 148 Lease Liabilities (1) 277 466 410 1,544 2,697 ( 1 ) Principal and interest, including current portion. ( 2 ) Refer to Note 35C for fair value assumptions .

Supplementary Cash Flow Informa

Supplementary Cash Flow Information	12 Months Ended
	Dec. 31, 2020
Disclosure Of Supplementary Cash Flow Information [Abstract]
Supplementary Cash Flow Information	37. SUPPLEMENTARY CASH FLOW INFORMATION The following table provides a reconciliation of liabilities to cash flows arising from financing activities: For the years ended December 31, 2020 2019 2018 Interest Paid 381 457 564 Interest Received 5 12 19 Income Taxes Paid 18 17 116 The following table provides a reconciliation of cash flows arising from financing activities: Dividends Payable Short-Term Borrowings Long-Term Debt Lease Liabilities As at December 31, 2017 - - 9,513 - Changes From Financing Cash Flows: Repayment of Long-Term Debt - - (1,144 ) - Net Issuance (Repayment) of Revolving Long-Term Debt - - (20 ) - Dividends Paid (245 ) - - - Non-Cash Changes: Dividends Declared 245 - - - Foreign Exchange (Gain) Loss - - 817 - Finance Costs - - (2 ) - As at December 31, 2018 - - 9,164 - Adjustment for Change in Accounting Policy (1) - - - 1,494 Changes From Financing Cash Flows: Dividends Paid (260 ) - - - Repayment of Long-Term Debt - - (2,279 ) - Net Issuance (Repayment) of Revolving Long-Term Debt - - 276 - Principal Repayment of Leases - - - (150 ) Non-Cash Changes: Dividends Declared 260 - - - Foreign Exchange (Gain) Loss - - (399 ) (23 ) Gain on Repurchase of Debt and Amortization of Debt Issuance Costs - - (63 ) - Lease Additions - - - 590 Re-measurement of Lease Liabilities - - - 15 Lease Terminations - - - (11 ) Other - - - 1 As at December 31, 2019 - - 6,699 1,916 Changes From Financing Cash Flows: Dividends Paid (77 ) - - - Issuance (Repayment) of Short-Term Borrowings - 117 - - Issuance of Long-Term Debt - - 1,326 - Repayment of Long-Term Debt - - (112 ) - Net Issuance (Repayment) of Revolving Long-Term Debt - - (220 ) - Principal Repayment of Leases - - - (197 ) Non-Cash Changes: Dividends Declared 77 - - - Foreign Exchange (Gain) Loss - 4 (231 ) (6 ) Gain on Repurchase of Debt and Amortization of Debt Issuance Costs - - (20 ) - Lease Additions - - - 49 Lease Terminations - - - (1 ) Lease Modifications - - - (2 ) Re-measurement of Lease Liabilities - - - (2 ) Other - - (1 ) - As at December 31, 2020 - 121 7,441 1,757 (1) Effective January 1, 2019, the Company adopted IFRS 16.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2020
Commitments And Contingencies [Abstract]
Commitments and Contingencies	38. COMMITMENTS AND CONTINGENCIES A) Commitments Future payments for the Company’s commitments are below. A commitment is an enforceable and legally binding agreement to make a payment in the future for the purchase of goods and services. These items exclude amounts recorded in the Consolidated Balance Sheets. As at December 31, 2020 1 Year 2 Years 3 Years 4 Years 5 Years Thereafter Total Transportation and Storage (1) 1,014 954 1,341 1,444 1,107 15,537 21,397 Real Estate (2) 34 36 38 41 44 604 797 Capital Commitments 1 2 - - - - 3 Other Long-Term Commitments 104 45 32 32 24 85 322 Total Payments (3) 1,153 1,037 1,411 1,517 1,175 16,226 22,519 As at December 31, 2019 1 Year 2 Years 3 Years 4 Years 5 Years Thereafter Total Transportation and Storage (1) 1,005 959 1,026 1,456 1,381 15,672 21,499 Real Estate (2) 35 36 38 39 42 662 852 Other Long-Term Commitments 104 44 36 34 28 108 354 Total Payments (3) 1,144 1,039 1,100 1,529 1,451 16,442 22,705 (1) Includes transportation commitments of $ 14 (2) Relates to the non-lease components of lease liabilities consisting of operating costs and unreserved parking for office space. Excludes committed payments for which a provision has been provided. ( 3 ) Contracts undertaken on behalf of WRB are reflected at Cenovus’s 50 percent interest. Transportation and storage commitments include future commitments relating to storage tank leases of $31 million, that have not yet commenced. As at December 31, 2020, there were outstanding letters of credit aggregating to $441 million issued as security for performance under certain contracts (2019 – $364 million). In addition to the above, Cenovus’s commitments related to its risk management program are disclosed in Note 36 and commitments related to the Arrangement are disclosed in Note 39. B) Contingencies Legal Proceedings Cenovus is involved in a limited number of legal claims associated with the normal course of operations. Cenovus believes that any liabilities that might arise from such matters, to the extent not provided for, are not likely to have a material effect on its Consolidated Financial Statements. Decommissioning Liabilities Cenovus is responsible for the retirement of long-lived assets at the end of their useful lives. Cenovus has recorded a liability of $1,248 million, based on current legislation and estimated costs, related to its upstream properties, refining facilities and the crude-by-rail terminal. Actual costs may differ from those estimated due to changes in legislation and changes in costs. Income Tax Matters The tax regulations and legislation and interpretations thereof in the various jurisdictions in which Cenovus operates are continually changing. As a result, there are usually a number of tax matters under review. Management believes that the provision for taxes is adequate. Contingent Payment In connection with the Acquisition in 2017, Cenovus agreed to make quarterly payments to ConocoPhillips during the five years subsequent to May 17, 2017 for quarters in which the average WCS crude oil price exceeds $52.00 per barrel during the quarter. As at December 31, 2020, the estimated fair value of the contingent payment was $ 63

Subsequent Event

Subsequent Event	12 Months Ended
	Dec. 31, 2020
Disclosure Of Nonadjusting Events After Reporting Period [Abstract]
Subsequent Event	39. SUBSEQUENT EVENT Cenovus and Husky Combine to Create a New Integrated Energy Company A) Summary of the Acquisition On October 25, 2020, Cenovus announced that it had entered into a definitive agreement to combine with Husky. The transaction was accomplished through a plan of arrangement pursuant to which Cenovus acquired all the issued and outstanding common shares of Husky in exchange for common shares and common share purchase warrants of Cenovus. In addition, all of the issued and outstanding Husky preferred shares were exchanged for Cenovus preferred shares with substantially identical terms. The Arrangement closed on January 1, 2021. The Arrangement will combine oil sands and heavy oil assets with extensive transportation, storage and logistics and downstream infrastructure, creating opportunities to optimize the margin captured across the heavy oil value chain. The combined company will be largely integrated, reducing exposure to Alberta heavy oil price differentials while maintaining exposure to global commodity prices. The Arrangement was accounted for using the acquisition method pursuant to IFRS 3, “ Business Combinations B) Purchase Price Allocation Cenovus acquired all the issued and outstanding Husky common shares in consideration for the issuance of 0.7845 Cenovus common shares plus 0.0651 Cenovus warrants for each Husky common share. Cenovus issued 788.5 6.1 the December 31, 2020 closing $7.75, as reported 65.4 $216 $519 million. The outstanding Husky stock options were also exchanged for Cenovus replacement stock options. Each replacement stock option entitles the holder to acquire 0.7845 of a Cenovus common share at an exercise price per share of a Husky stock option divided by 0.7845. The fair value of the replacement stock options was estimated to be $9 million The preliminary purchase price allocation is based on Management’s best estimate of the assets acquired and liabilities assumed. Upon finalizing the value of net assets acquired, adjustments may be required. The following table summarizes the details of the consideration and the recognized amounts of assets acquired and liabilities assumed at the date of the acquisition. As at January 1, 2021 Consideration Common Shares 6,111 Preferred Shares 519 Share Purchase Warrants 216 Replacement Stock Options 9 Non-Controlling Interest 11 Total Consideration and Non-Controlling Interest 6,866 Identifiable Assets Acquired and Liabilities Assumed Cash 735 Restricted Cash 164 Accounts Receivable and Accrued Revenues 1,272 Inventories 1,118 Property, Plant and Equipment, Intangible Assets and Deferred Income Tax Assets 15,227 Right-of-Use Assets 1,137 Long-Term Income Tax Receivable 202 Other Assets 200 Investments in Joint Ventures 457 Accounts Payable and Accrued Liabilities (2,224 ) Income Tax Payable (59 ) Current Portion of Long-Term Debt (40 ) Long-Term Debt (6,602 ) Lease Liabilities (1,447 ) Decommissioning Liabilities (2,835 ) Other Liabilities (439 ) Total Identifiable Net Assets 6,866 The fair value of trade and other receivables acquired as part of the acquisition is $ 1.1 Cenovus incurred $29 million of acquisition related costs, excluding common share, preferred share and warrant issuance costs. These costs have been included in transaction costs in the Consolidated Statements of Earnings (Loss). C) Liquidity and Commitments Subsequent to the closing of the Arrangement on January 1, 2021, Cenovus obtained access to additional sources of liquidity including: $735 million in cash, $3.7 billion available on Husky’s committed credit facilities and $508 million available on Husky’s uncommitted demand facilities. Husky’s committed credit facilities have a capacity of $4.0 billion and its uncommitted demand facilities have a capacity of $975 million, of which $850 million may be drawn for general purposes, or the full amount can be available to issue letters of credit. The Arrangement resulted in the assumption of Husky’s non-cancellable contracts and other commercial commitments. As at January 1, 2021, total commitments assumed by Cenovus were $ 18.7 $7.4 billion $1.7 D) Segmented Disclosures Management is in the process of finalizing the determination of the operating and reporting segments for the Company. It is anticipated that the Company’s business will be conducted predominately through an upstream and downstream segment. Management continues to evaluate how the segments may be presented and will make a final determination during the first quarter of 2021. The upstream business is anticipated to be reported as follows: • Oil Sands, includes the development and production of heavy oil and bitumen in northeast Alberta and Saskatchewan. Cenovus’s oil sands assets include Foster Creek, Christina Lake, Sunrise and Tucker oil sands projects, as well as Lloydminster Thermal and Cold and Enhanced Oil Recovery assets. • Conventional, includes the operations from conventional oil and natural gas production, including processing operations in the Deep Basin and other parts of Western Canada. • Offshore, includes the offshore operations, exploration and development activities in the Asia Pacific region and Atlantic Canada region. The downstream business is anticipated to be reported as follows: • Canadian Manufacturing, includes Cenovus’s owned and operated upgrader and asphalt refinery in Lloydminster, the owned and operated crude-by-rail terminal and two ethanol plants. • Retail, includes the Canadian retail, commercial and wholesale channels. • U.S. Manufacturing, includes the U.S. operations of wholly owned refineries in Lima and Superior, the jointly owned Wood River and Borger refineries with operator Phillips 66 and the jointly owned Toledo refinery with BP Products North America Inc. as operator.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2020
Disclosure Of Summary Of Significant Accounting Policies [Abstract]
Principles of Consolidation	A) Principles of Consolidation The Consolidated Financial Statements include the accounts of Cenovus and its subsidiaries. Subsidiaries are entities over which the Company has control. Subsidiaries are consolidated from the date of acquisition of control and continue to be consolidated until the date that there is a loss of control. All intercompany transactions, balances, and unrealized gains and losses from intercompany transactions are eliminated on consolidation. Interests in joint arrangements are classified as either joint operations or joint ventures, depending on the rights and obligations of the parties to the arrangement. Joint operations arise when the Company has rights to the assets and obligations for the liabilities of the arrangement. The Company’s refining activities are conducted through the joint operation WRB Refining LP (“WRB”) and, accordingly, the accounts reflect the Company’s share of the assets, liabilities, revenues and expenses. An associate is an entity for which the Company has significant influence over but does not control or jointly control the investee. Investments in associates are accounted for using the equity method of accounting and are recognized at cost and adjusted thereafter to recognize the Company’s share of the investee’s profit or loss and other comprehensive income (“OCI”).
Foreign Currency Translation	B) Foreign Currency Translation Functional and Presentation Currency The Company’s functional and presentation currency is Canadian dollars. The accounts of the Company’s foreign operations that have a functional currency different from the Company’s presentation currency are translated into the Company’s presentation currency at period-end exchange rates for assets and liabilities, and using average rates over the period for revenues and expenses. Translation gains and losses relating to the foreign operations are recognized in OCI as cumulative translation adjustments. When the Company disposes of an entire interest in a foreign operation or loses control, joint control, or significant influence over a foreign operation, the foreign currency gains or losses accumulated in OCI related to the foreign operation are recognized in net earnings. When the Company disposes of part of an interest in a foreign operation that continues to be a subsidiary, a proportionate amount of gains and losses accumulated in OCI is allocated between controlling and non-controlling interests. Transactions and Balances Transactions in foreign currencies are translated to the respective functional currencies at exchange rates in effect at the dates of the transactions.
Revenue Recognition	C) Revenue Recognition Revenue is measured based on the consideration specified in a contract with a customer and excludes amounts collected on behalf of third parties. Cenovus recognizes revenue when it transfers control of the product or service to a customer, which is generally when title passes from the Company to its customer. Purchases and sales of products that are entered into in contemplation of each other with the same counterparty are recorded on a net basis. Revenues associated with services provided as agent are recorded as the services are provided. Cenovus recognizes revenue from the following major products and services: • Sale of crude oil, NGLs and natural gas. • Sale of petroleum and refined products. • Natural gas processing revenue. • Marketing and transportation services. • Fee-for-service hydrocarbon trans-loading services. The Company satisfies its performance obligations in contracts with customers upon the delivery of crude oil, NGLs, natural gas and petroleum and refined products, which is generally at a point in time. Performance obligations for natural gas processing revenue, marketing, transportation services and trans-loading services are satisfied over time as the service is provided. Cenovus sells its production of crude oil, NGLs, natural gas and petroleum and refined products generally pursuant to variable price contracts. The transaction price for variable price contracts is based on the commodity price, adjusted for quality, location and other factors. The amount of revenue recognized is based on the agreed transaction price with any variability in transaction price recognized in the same period. Revenue associated with natural gas processing, marketing, transportation services and trans-loading services are based, generally on fixed price contracts. Cenovus’s revenue transactions do not contain significant financing components and payments are typically due within 30 days of revenue recognition. The Company does not adjust transaction prices for the effects of a significant financing component when the period between the transfer of the promised goods or services to the customer and payment by the customer is less than one year. The Company does not disclose or quantify information about remaining performance obligations that have an original expected duration of one year or less and it does not have any long-term contracts with unfulfilled performance obligations.
Transportation and Blending	D) Transportation and Blending The costs associated with the transportation of crude oil, NGLs and natural gas, including the cost of diluent used in blending, are recognized when the product is sold.
Exploration Expense	E) Exploration Expense Costs incurred prior to obtaining the legal right to explore (pre-exploration costs) are expensed in the period in which they are incurred as exploration expense. Costs incurred after the legal right to explore is obtained are initially capitalized. If it is determined that the field/project/area is not technically feasible and commercially viable or if the Company decides not to continue the exploration and evaluation activity, the unrecoverable accumulated costs are expensed as exploration expense.
Employee Benefit Plans	F) Employee Benefit Plans The Company provides employees with a pension plan that includes either a defined contribution or defined benefit component and an other post-employment benefit plan (“OPEB”). Pension expense for the defined contribution pension is recorded as the benefits are earned. The cost of the defined benefit pension and OPEB plans are actuarially determined using the projected unit credit method. The amount recognized in other liabilities on the Consolidated Balance Sheets for the defined benefit pension and OPEB plans is the present value of the defined benefit obligation less the fair value of plan assets. Any surplus resulting from this calculation is limited to the present value of any economic benefits available in the form of refunds from the plans or reductions in future contributions to the plans. Changes in the defined benefit obligation from service costs, net interest and remeasurements are recognized as follows: • Service costs, including current service costs, past service costs, gains and losses on curtailments, and settlements, are recorded with pension benefit costs. • Net interest is calculated by applying the same discount rate used to measure the defined benefit obligation at the beginning of the annual period to the net defined benefit asset or liability measured. Interest expense and interest income on net post-employment benefit liabilities and assets are recorded with pension benefit costs in operating, and general and administrative expenses, as well as PP&E and E&E assets. • Remeasurements, composed of actuarial gains and losses, the effect of changes to the asset ceiling (excluding interest) and the return on plan assets (excluding interest income), are charged or credited to equity in OCI in the period in which they arise. Remeasurements are not reclassified to net earnings in subsequent periods. Pension benefit costs are recorded in operating, and general and administrative expenses, as well as PP&E and E&E assets, corresponding to where the associated salaries of the employees rendering the service are recorded. From time-to-time, the Company may provide certain other long-term incentive benefits to employees. In 2019, a one-time incentive program was introduced whereby a cash award equivalent to the employee’s base salary is payable if Cenovus achieves prior to February 12, 2024 a target share price of $20 per share for a period of 20 consecutive trading days on the TSX (the “Plan”). All employees, except for the President & Chief Executive Officer, are eligible and new employees are eligible for a pro-rated award based on start date provided they are employed on the payout date. The obligation related to this Plan is estimated as the probability of the payout being achieved multiplied by the expected payout amount. The obligation is recognized over the greater of (i) the time to earliest payout of February 13, 2022; and (ii) the estimated time until payout is achieved, prior to February 12, 2024 as general and administrative expense.
Government Grants	G) Government Grants Government grants are recognized when there is reasonable assurance that the grant will be received and all conditions associated with the grant are met. Grants related to assets are recorded as a reduction to the asset’s carrying value and are depreciated over the useful life of the asset. Claims under government grant programs related to income are recorded as other income in the period in which eligible expenses were incurred or when the services have been performed.
Income Taxes	H) Income Taxes Income taxes comprise current and deferred taxes. Income taxes are provided for on a non-discounted basis at amounts expected to be paid using the tax rates and laws that have been enacted or substantively enacted at the Consolidated Balance Sheet date. Cenovus follows the liability method of accounting for income taxes, where deferred income taxes are recorded for the effect of any temporary difference between the accounting and income tax basis of an asset or liability, using the substantively enacted income tax rates expected to apply when the assets are realized or liabilities are settled. Deferred income tax balances are adjusted to reflect changes in income tax rates that are substantively enacted with the adjustment being recognized in net earnings in the period that the change occurs, except when it relates to items charged or credited directly to equity or OCI, in which case the deferred income tax is also recorded in equity or OCI, respectively. Deferred income tax is recognized on temporary differences arising from investments in subsidiaries except in the case where the timing of the reversal of the temporary difference is controlled by the Company and it is probable that the temporary difference will not reverse in the foreseeable future or when distributions can be made without incurring income taxes. Deferred income tax assets are recognized only to the extent that it is probable that future taxable profit will be available against which the temporary differences can be utilized. Deferred income tax assets and liabilities are only offset where they arise within the same entity and tax jurisdiction. Deferred income tax assets and liabilities are presented as non-current.
Net Earnings per Share Amounts	I) Net Earnings per Share Amounts Basic net earnings per share is computed by dividing net earnings by the weighted average number of common shares outstanding during the period. Diluted net earnings per share is calculated giving effect to the potential dilution that would occur if stock options or other contracts to issue common shares were exercised or converted to common shares. The treasury stock method is used to determine the dilutive effect of stock options and other dilutive instruments. The treasury stock method assumes that proceeds received from the exercise of in-the-money stock options are used to repurchase common shares at the average market price. For those contracts that may be settled in cash or in shares at the holder’s option, the more dilutive of cash settlement and share settlement is used in calculating diluted earnings per share.
Cash and Cash Equivalents	J) Cash and Cash Equivalents Cash and cash equivalents include short-term investments, such as money market deposits or similar type instruments, with a maturity of three months or less.
Inventories	K) Inventories Product inventories are valued at the lower of cost and net realizable value on a first-in, first-out or weighted average cost basis. The cost of inventory includes all costs incurred in the normal course of business to bring each product to its present location and condition. Net realizable value is the estimated selling price in the ordinary course of business less any expected selling costs. If the carrying amount exceeds net realizable value, a write-down is recognized. The write-down may be reversed in a subsequent period if circumstances which caused it no longer exist and the inventory is still on hand.
Exploration and Evaluation Assets	L) Exploration and Evaluation Assets Costs incurred after the legal right to explore an area has been obtained, and before technical feasibility and commercial viability of the field/project/area have been established, are capitalized as E&E assets. These costs include license acquisition, geological and geophysical, drilling, sampling, decommissioning and other directly attributable internal costs. E&E assets are carried forward until technical feasibility and commercial viability of the field/project/area is established or the assets are determined to be impaired or the future economic value has decreased. E&E costs are subject to regular technical, commercial and Management review to confirm the continued intent to develop the resources. Assets classified as E&E may have sales of crude oil, NGLs or natural gas prior to the reclassification to PP&E. These operating results are recognized in the Consolidated Statements of Earnings (Loss). A depletion charge, recorded as depreciation, depletion and amortization (“DD&A”), is recognized on this production using a unit-of-production method based on estimated proved reserves determined using forward prices and costs and considering any estimated future costs to be incurred in developing the proved reserves. Natural gas reserves are converted on an energy equivalent basis. Non-producing assets classified as E&E are not depleted. Once technical feasibility and commercial viability have been established, the carrying value of the E&E asset is tested for impairment. The carrying value, net of any impairment loss, is then reclassified as PP&E. Any gains or losses from the divestiture of E&E assets are recognized in net earnings.
Property, Plant and Equipment	M) Property, Plant and Equipment General PP&E is stated at cost less accumulated DD&A, and net of any impairment losses. Expenditures related to renewals or betterments that improve the productive capacity or extend the life of an asset are capitalized. Maintenance and repairs are expensed as incurred. Land is not depreciated. Any gains or losses from the divestiture of PP&E are recognized in net earnings. Development and Production Assets Development and production assets are capitalized on an area-by-area basis and include all costs associated with the development and production of crude oil and natural gas properties, as well as any E&E expenditures incurred in finding reserves of crude oil, NGLs or natural gas transferred from E&E assets. Capitalized costs include directly attributable internal costs, decommissioning liabilities and, for qualifying assets, borrowing costs directly associated with the acquisition of, the exploration for, and the development of crude oil and natural gas reserves. Costs accumulated within each area are depleted using the unit-of-production method based on estimated proved reserves determined using forward prices and costs. For the purpose of this calculation, natural gas is converted to crude oil on an energy equivalent basis. Costs subject to depletion include estimated future costs to be incurred in developing proved reserves. Exchanges of development and production assets are measured at fair value unless the transaction lacks commercial substance or the fair value of neither the asset received, nor the asset given up, can be reliably measured. When fair value is not used, the carrying amount of the asset given up is used as the cost of the asset acquired. Other Upstream Assets Other upstream assets include information technology assets used to support the upstream business. These assets are depreciated on a straight-line basis over their useful lives of three years. Other upstream assets also include gross overriding royalty interests (“GORRs”) in certain oil and gas properties and are depleted using a unit-of-production method. Refining Assets The initial acquisition costs of refining PP&E are capitalized when incurred. Costs include the cost of constructing or otherwise acquiring the equipment or facilities, the cost of installing the asset and making it ready for its intended use, the associated decommissioning costs and, for qualifying assets, borrowing costs. Refining assets are depreciated on a straight-line basis over the estimated service life of each component of the refinery. The major components are depreciated as follows: Land improvements and buildings 25 to 40 years Office equipment and vehicles 3 to 15 years Refining equipment 10 to 60 years The residual value, the method of amortization and the useful life of each component are reviewed annually and adjusted on a prospective basis, if appropriate. Other Assets Costs associated with the crude-by-rail terminal, infrastructure, office furniture, fixtures, leasehold improvements, information technology and aircraft are carried at cost and depreciated on a straight-line basis over the estimated service lives of the assets, which range from three years to 60 years. The residual value, the method of amortization and the useful lives of the assets are reviewed annually and adjusted on a prospective basis, if appropriate.
Impairment of Non-Financial Assets	N) Impairment of Non-Financial Assets PP&E, E&E assets and ROU assets are reviewed separately for indicators of impairment quarterly or when facts and circumstances suggest that the carrying amount may exceed its recoverable amount. Goodwill is tested for impairment at least annually. If indicators of impairment exist, the recoverable amount of the asset or cash-generating unit (“CGU”) is estimated as the greater of value-in-use (“VIU”) and fair value less costs of disposal (“FVLCOD”). VIU is estimated as the present value of the future cash flows expected to arise from the continuing use of a CGU or an asset. FVLCOD is the amount that would be realized from the disposition of an asset or CGU in an arm’s length transaction between knowledgeable and willing parties. For Cenovus’s upstream assets, FVLCOD is based on the discounted after-tax cash flows of reserves and resources using forward prices and costs, consistent with Cenovus’s independent qualified reserves evaluators (“IQREs”) and may consider an evaluation of comparable asset transactions. E&E assets are allocated to a related CGU containing development and production assets for the purposes of testing for impairment. ROU assets may be tested as part of a CGU, as a separate CGU or as an individual asset. Goodwill is allocated to the CGUs to which it contributes to the future cash flows. If the recoverable amount of the CGU is less than the carrying amount, an impairment loss is recognized. An impairment loss is allocated first to reduce the carrying amount of any goodwill allocated to the CGU and then to reduce the carrying amounts of the other assets in the CGU. Goodwill impairments are not reversed. Impairment losses on PP&E and ROU assets are recognized in the Consolidated Statements of Earnings (Loss) as additional DD&A and E&E asset impairments or write-downs are recognized as exploration expense. Impairment losses recognized in prior periods, other than goodwill impairments, are assessed at each reporting date for any indicators that the impairment losses may no longer exist or may have decreased. In the event that an impairment loss reverses, the carrying amount of the asset is increased to the revised estimate of its recoverable amount, but only to the extent that the carrying amount does not exceed the amount that would have been determined had no impairment loss been recognized on the asset in prior periods. The amount of the reversal is recognized in net earnings.
Leases	O) Leases The Company adopted IFRS 16, “ Lease Policy Applicable From January 1, 2019 Leases The Company assesses whether a contract is a lease based on whether the contract conveys the right to control the use of an underlying asset for a period of time in exchange for consideration. The Company allocates the consideration in the contract to each lease component on the basis of their relative stand-alone prices. However, for the leases of storage tanks, the Company has elected not to separate non-lease components. As Lessee Leases are recognized as a ROU asset and a corresponding lease liability at the date on which the leased asset is available for use by the Company. Assets and liabilities arising from a lease are initially measured on a present value basis. Lease liabilities include the net present value of fixed payments, costs to be incurred by the lessee in dismantling, removing and restoring the underlying asset, variable lease payments that are based on an index or a rate, amounts expected to be paid by the lessee under residual value guarantees, the exercise price of purchase options if the lessee is reasonably certain to exercise that option, and payments of penalties for terminating the lease, less any lease incentives receivable. These payments are discounted using the Company’s incremental borrowing rate when the rate implicit in the lease is not readily available. The Company uses a single discount rate for a portfolio of leases with reasonably similar characteristics. Lease payments are allocated between the liability and finance costs. The finance cost is charged to net earnings over the lease term. The lease liability is measured at amortized cost using the effective interest method. It is remeasured when there is a change in the future lease payments arising from a change in an index or rate, if there is a change in the amount expected to be payable under a residual value guarantee or if there is a change in the assessment of whether the Company will exercise a purchase, extension or termination option that is within the control of the Company. When the lease liability is remeasured, a corresponding adjustment is made to the carrying amount of the ROU asset or is recorded in the Consolidated Statements of Earnings (Loss) if the carrying amount of the ROU asset has been reduced to zero. The ROU asset is initially measured at cost, which comprises the initial amount of the lease liability any initial direct costs incurred and an estimate of costs to dismantle and remove the underlying asset or to restore the underlying asset or site on which it is located less any lease payments made at or before the commencement date. The ROU asset is depreciated, on a straight-line basis, over the shorter of the estimated useful life of the asset or the lease term. The ROU asset may be adjusted for certain remeasurements of the lease liability and impairment losses. Leases that have terms of less than twelve months or leases on which the underlying asset is of low value are recognized as an expense in the Consolidated Statements of Earnings (Loss) on a straight-line basis over the lease term. A lease modification will be accounted for as a separate lease if the modification increases the scope of the lease and if the consideration for the lease increases by an amount commensurate with the stand-alone price for the increase in scope. For a modification that is not a separate lease or where the increase in consideration is not commensurate, at the effective date of the lease modification, the Company will remeasure the lease liability using the Company’s incremental borrowing rate, when the rate implicit to the lease is not readily available, with a corresponding adjustment to the ROU asset. A modification that decreases the scope of the lease will be accounted for by decreasing the carrying amount of the ROU asset, and recognizing a gain or loss in net earnings that reflects the proportionate decrease in scope. As Lessor As a lessor, the Company assesses at inception whether a lease is a finance or operating lease. Leases where the Company transfers substantially all of the risk and rewards incidental to ownership of the underlying asset are classified as financing leases. Under a finance lease, the Company recognizes a receivable at an amount equal to the net investment in the lease which is the present value of the aggregate of lease payments receivable by the lessor. If substantially all the risks and rewards of ownership of an asset are not transferred the lease is classified as an operating lease. The Company recognizes lease payments received under operating leases as income on a straight-line basis over the lease term as other income. When the Company is an intermediate lessor, it accounts for its interest in the head lease and the sublease separately. It assesses the lease classification of a sublease with reference to the ROU asset from the head lease not with reference to the underlying assets. If the head lease is a short-term lease to which the Company applies the exemption for lease accounting, the sublease is classified as an operating lease. Policy Applicable Before January 1, 2019 Leases in which substantially all of the risks and rewards of ownership are retained by the lessor are classified as operating leases. Operating lease payments are recognized as an expense on a straight-line basis over the lease term. Leases where the Company assumes substantially all the risks and rewards of ownership are classified as finance leases. At inception, a leased asset within PP&E and a corresponding lease obligation are recognized. The leased asset is depreciated over the shorter of the estimated useful life of the asset or the lease term.
Intangible Assets	P) Intangible Assets Intangible assets acquired separately are initially measured at cost. Following initial recognition, intangible assets are recognized at cost less any accumulated amortization and accumulated impairment losses. Intangible assets with finite lives are amortized over the useful life and assessed for impairment whenever there is an indication that the intangible asset may be impaired. The amortization expense on intangible assets is recognized in the
Business Combinations and Goodwill	Q) Business Combinations and Goodwill Business combinations are accounted for using the acquisition method of accounting in which the identifiable assets acquired, liabilities assumed and non-controlling interest, if any, are recognized and measured at their fair value at the date of acquisition, with the exception of income taxes, stock-based compensation, lease liabilities and ROU assets. Any excess of the purchase price plus any non-controlling interest over the value of the net assets acquired is recognized as goodwill. Any deficiency of the purchase price over the value of the net assets acquired is credited to net earnings. At acquisition, goodwill is allocated to each of the CGUs to which it relates. Subsequent measurement of goodwill is at cost less any accumulated impairment losses. Contingent consideration transferred in a business combination is measured at fair value on the date of acquisition and classified as a financial liability or equity. Contingent consideration classified as a liability is re-measured at fair value at each reporting date, with changes in fair value recognized in net earnings. Payments are classified as cash used in investing activities until the cumulative payments exceed the acquisition date fair value of the liability. Cumulative payments in excess of the acquisition date fair value are classified as cash used in operating activities. Contingent consideration classified as equity are not re-measured and settlements are accounted for within equity. When a business combination is achieved in stages, the Company re-measures its pre-existing interest at the acquisition date fair value and recognizes the resulting gain or loss, if any, in net earnings.
Provisions	R) Provisions General A provision is recognized if, as a result of a past event, the Company has a present obligation, legal or constructive, that can be estimated reliably, and it is more likely than not that an outflow of economic benefits will be required to settle the obligation. Where applicable, provisions are determined by discounting the expected future cash flows at a pre-tax credit-adjusted rate that reflects the current market assessments of the time value of money and the risks specific to the liability. The increase in the provision due to the passage of time is recognized as a finance cost in the Consolidated Statements of Earnings (Loss). Decommissioning Liabilities Decommissioning liabilities include those legal or constructive obligations where the Company will be required to retire tangible long-lived assets such as producing well sites, upstream processing facilities, refining facilities and the crude-by-rail terminal. The amount recognized is the present value of estimated future expenditures required to settle the obligation using a credit-adjusted risk-free rate. A corresponding asset equal to the initial estimate of the liability is capitalized as part of the cost of the related long-lived asset. Changes in the estimated liability resulting from revisions to expected timing or future decommissioning costs are recognized as a change in the decommissioning liability and the related long-lived asset. The amount capitalized in PP&E is depreciated over the useful life of the related asset. Actual expenditures incurred are charged against the accumulated liability. Onerous Contract Provisions Onerous contract provisions are recognized when the unavoidable costs of meeting the obligation exceed the economic benefit derived from the contract. The provision for onerous contracts is measured at the present value of estimated future cash flows underlying the obligations less any estimated recoveries, discounted at the credit-adjusted risk-free rate. Changes in the underlying assumptions are recognized in the Consolidated Statements of Earnings (Loss).
Share Capital	S) Share Capital Common shares are classified as equity. Transaction costs directly attributable to the issue of common shares are recognized as a deduction from equity, net of any income taxes.
Stock-Based Compensation	T) Stock-Based Compensation Net Settlement Rights NSRs are accounted for as equity instruments, which are measured at fair value on the grant date using the Black-Scholes-Merton valuation model and are not revalued at each reporting date. The fair value is recognized as stock-based compensation costs over the vesting period, with a corresponding increase recorded as paid in surplus in Shareholders’ Equity. On exercise, the cash consideration received by the Company and the associated paid in surplus are recorded as share capital. PSUs, RSUs and DSUs are accounted for as liability instruments and are measured at fair value based on the market value of Cenovus’s common shares at each period end. The fair value is recognized as stock-based compensation costs over the vesting period. Fluctuations in the fair values are recognized as stock-based compensation costs in the period they occur.
Financial Instruments	U) Financial Instruments The Company’s financial assets include cash and cash equivalents, accounts receivable and accrued revenues, risk management assets, net investment in finance leases, investments in the equity of private companies and long-term receivables. The Company’s financial liabilities include accounts payable and accrued liabilities, short-term borrowings, lease liabilities, contingent payment, risk management liabilities and long-term debt. Financial instruments are recognized when the Company becomes a party to the contractual provisions of the instrument. Financial assets and liabilities are not offset unless the Company has the current legal right to offset and intends to settle on a net basis or settle the asset and liability simultaneously. The Company characterizes its fair value measurements into a three-level hierarchy depending on the degree to which the inputs are observable, as follows: • Level 1 inputs are quoted prices in active markets for identical assets and liabilities. • Level 2 inputs are inputs, other than quoted prices included within Level 1, that are observable for the asset or liability either directly or indirectly. • Level 3 inputs are unobservable inputs for the asset or liability. Classification and Measurement of Financial Assets The initial classification of a financial asset depends upon the Company’s business model for managing its financial assets and the contractual terms of the cash flows. There are three measurement categories into which the Company classified its financial assets: • Amortized Cost: Includes assets that are held within a business model whose objective is to hold assets to collect contractual cash flows and its contractual terms give rise on specified dates to cash flows that represent solely payments of principal and interest. • FVOCI: Includes assets that are held within a business model whose objective is achieved by both collecting contractual cash flows and selling the financial assets, where its contractual terms give rise on specified dates to cash flows that represent solely payments of principal and interest. • Fair Value through Profit or Loss (“FVTPL”): Includes assets that do not meet the criteria for amortized cost or FVOCI and are measured at fair value through profit or loss. This includes all derivative financial assets. On initial recognition, the Company may irrevocably designate a financial asset that meets the amortized cost or FVOCI criteria as measured at FVTPL if doing so eliminates or significantly reduces an accounting mismatch. On initial recognition of an equity investment that is not held-for-trading, the Company may irrevocably elect to present subsequent changes in the investment’s fair value in OCI. There is no subsequent reclassification of fair value changes to earnings following the derecognition of the investment. However, dividends that reflect a return on investment continue to be recognized in net earnings. This election is made on an investment-by-investment basis. At initial recognition, the Company measures a financial asset at its fair value and, in the case of a financial asset not at FVTPL, including transaction costs that are directly attributable to the acquisition of the financial asset. Transaction costs of financial assets carried at FVTPL are recorded as an expense in net earnings. Financial assets are reclassified subsequent to their initial recognition only if the business model for managing those financial assets changes. The affected financial assets will be reclassified on the first day of the first reporting period following the change in the business model. A financial asset is derecognized when the rights to receive cash flows from the asset have expired or have been transferred and the Company has transferred substantially all the risks and rewards of ownership. Impairment of Financial Assets The Company recognizes loss allowances for expected credit losses (“ECLs”) on its financial assets measured at amortized cost. Due to the nature of its financial assets, Cenovus measures loss allowances at an amount equal to expected lifetime ECLs. Lifetime ECLs are the anticipated ECLs that result from all possible default events over the expected life of a financial asset. ECLs are a probability-weighted estimate of credit losses. Credit losses are measured as the present value of all cash shortfalls (i.e. the difference between the cash flows due to the entity in accordance with the contract and the cash flows that the Company expects to receive). ECLs are discounted at the effective interest rate of the related financial asset. The Company does not have any financial assets that contain a financing component. Classification and Measurement of Financial Liabilities A financial liability is initially classified as measured at amortized cost or FVTPL. A financial liability is classified as measured at FVTPL if it is held-for-trading, a derivative, or designated as FVTPL on initial recognition. The classification of a financial liability is irrevocable. Financial liabilities at FVTPL (other than financial liabilities designated at FVTPL) are measured at fair value with changes in fair value, along with any interest expense, recognized in net earnings. Other financial liabilities are initially measured at fair value less directly attributable transaction costs and are subsequently measured at amortized cost using the effective interest method. Interest expense and foreign exchange gains and losses are recognized in net earnings. Any gain or loss on derecognition is also recognized in net earnings. A financial liability is derecognized when the obligation is discharged, cancelled or expired. When an existing financial liability is replaced by another from the same counterparty with substantially different terms, or the terms of an existing liability are substantially modified, it is treated as a derecognition of the original liability and the recognition of a new liability. When the terms of an existing financial liability are altered, but the changes are considered non-substantial, it is accounted for as a modification to the existing financial liability. Where a liability is substantially modified it is considered to be extinguished and a gain or loss is recognized in net earnings based on the difference between the carrying amount of the liability derecognized and the fair value of the revised liability. Where a liability is modified in a non-substantial way, the amortized cost of the liability is remeasured based on the new cash flows and a gain or loss is recorded in net earnings. Derivatives Derivative financial instruments are used to manage economic exposure to market risks relating to commodity prices, foreign currency exchange rates and interest rates. Policies and procedures are in place with respect to required documentation and approvals for the use of derivative financial instruments. Where specific financial instruments are executed, the Company assesses, both at the time of purchase and on an ongoing basis, whether the financial instrument used in the particular transaction is effective in offsetting changes in fair values or cash flows of the transaction. Derivative financial instruments are measured at FVTPL unless designated for hedge accounting. Derivative instruments that do not qualify as hedges, or are not designated as hedges, are recorded using mark-to-market accounting whereby instruments are recorded in the Consolidated Balance Sheets as either an asset or liability with changes in fair value recognized in net earnings as a gain or loss on risk management. The estimated fair value of all derivative instruments is based on quoted market prices or, in their absence, third-party market indications and forecasts.
Reclassification	V) Reclassification Certain information provided for prior years has been reclassified to conform to the presentation adopted in 2020.
Recent Accounting Pronouncements	W) Recent Accounting Pronouncements New Accounting Standards and Interpretations not yet Adopted There are new accounting standards, amendments to accounting standards and interpretations that are effective for annual periods beginning on or after January 1, 2021 and have not been applied in preparing the Consolidated Financial Statements for the year ended December 31, 2020. These standards and interpretations are not expected to have a material impact on the Company’s Consolidated Financial Statements. The standard applicable to Cenovus is as follows and will be adopted on its effective date: Interest Rate Benchmark Reform On August 27, 2020, the IASB published Interest Rate Benchmark Reform – Phase 2 (Amendments to IFRS 9, “ Financial Instruments Financial Instruments: Recognition and Measurement Financial Instruments: Disclosure Insurance Contracts

Description of Business and S_2

Description of Business and Segmented Disclosures (Tables)	12 Months Ended
	Dec. 31, 2020
Disclosure Of Reportable Segments [Abstract]
Schedule of Segment and Operational Information	A) Results of Operations – Segment and Operational Information Oil Sands Conventional Refining and Marketing For the years ended December 31, 2020 2019 2018 2020 2019 2018 2020 2019 2018 Revenues Gross Sales 7,514 10,838 10,026 635 691 904 6,051 10,513 11,183 Less: Royalties 324 1,143 473 40 30 73 - - - 7,190 9,695 9,553 595 661 831 6,051 10,513 11,183 Expenses Purchased Product - - - - - - 5,397 8,795 9,201 Transportation and Blending 4,399 5,152 5,879 81 82 90 - - - Operating 1,094 1,039 1,037 318 337 403 824 948 927 Inventory Write-Down (Reversal) 316 - - - - - 239 49 60 (Gain) Loss on Risk Management 268 23 1,551 - - 26 (21 ) (16 ) (1 ) Operating Margin 1,113 3,481 1,086 196 242 312 (388 ) 737 996 Depreciation, Depletion and Amortization 1,684 1,543 1,439 880 319 412 739 280 222 Exploration Expense 9 18 6 82 64 2,117 - - - Segment Income (Loss) (580 ) 1,920 (359 ) (766 ) (141 ) (2,217 ) (1,127 ) 457 774 Corporate and Eliminations Consolidated For the years ended December 31, 2020 2019 2018 2020 2019 2018 Revenues Gross Sales (609 ) (689 ) (724 ) 13,591 21,353 21,389 Less: Royalties - - - 364 1,173 546 (609 ) (689 ) (724 ) 13,227 20,180 20,843 Expenses Purchased Product (278 ) (417 ) (517 ) 5,119 8,378 8,684 Transportation and Blending (36 ) (50 ) (27 ) 4,444 5,184 5,942 Operating (306 ) (236 ) (183 ) 1,930 2,088 2,184 Inventory Write-Down (Reversal) - - - 555 49 60 (Gain) Loss on Risk Management 61 149 (1,271 ) 308 156 305 Depreciation, Depletion and Amortization 161 107 58 3,464 2,249 2,131 Exploration Expense - - - 91 82 2,123 Segment Income (Loss) (211 ) (242 ) 1,216 (2,684 ) 1,994 (586 ) General and Administrative 292 331 1,020 292 331 1,020 Finance Costs 536 511 627 536 511 627 Interest Income (9 ) (12 ) (19 ) (9 ) (12 ) (19 ) Transaction Costs 29 - - 29 - - Foreign Exchange (Gain) Loss, Net (181 ) (404 ) 854 (181 ) (404 ) 854 Re-measurement of Contingent Payment (80 ) 164 50 (80 ) 164 50 (Gain) Loss on Divestiture of Assets (81 ) (2 ) 795 (81 ) (2 ) 795 Other (Income) Loss, Net 40 9 13 40 9 13 546 597 3,340 546 597 3,340 Earnings (Loss) From Continuing Operations Before Income Tax (3,230 ) 1,397 (3,926 ) Income Tax Expense (Recovery) (851 ) (797 ) (1,010 ) Net Earnings (Loss) From Continuing Operations (2,379 ) 2,194 (2,916 )
Schedule of Revenues by Product	B) Revenues by Product For the years ended December 31, 2020 2019 2018 Upstream Crude Oil 7,270 9,790 9,662 NGLs 142 202 333 Natural Gas 315 299 320 Other 58 65 69 Refined Products 4,734 8,291 9,032 Market Optimization 1,317 2,222 2,151 Corporate and Eliminations (609 ) (689 ) (724 ) Revenues From Continuing Operations 13,227 20,180 20,843
Schedule of Geographical Information	C) Geographical Information Revenues For the years ended December 31, 2020 2019 2018 Canada 8,399 11,798 11,694 United States 4,828 8,382 9,149 Consolidated 13,227 20,180 20,843 Non-Current Assets (1) As at December 31, 2020 2019 Canada 26,168 28,336 United States 3,590 4,093 Consolidated 29,758 32,429 (1) Includes exploration and evaluation (“E&E”) assets, property, plant and equipment (“PP&E”), right-of-use (“ROU”) assets, other assets and goodwill.
Schedule of Assets by Segment	D) Assets by Segment E&E Assets (1) PP&E ROU Assets As at December 31, 2020 2019 2020 2019 2020 2019 Oil Sands 617 594 19,748 20,924 623 768 Conventional 6 193 1,758 2,433 3 3 Refining and Marketing - - 3,652 4,131 79 77 Corporate and Eliminations - - 253 346 434 477 Consolidated 623 787 25,411 27,834 1,139 1,325 Goodwill Total Assets As at December 31, 2020 2019 2020 2019 Oil Sands 2,272 2,272 24,656 26,203 Conventional - - 1,953 2,754 Refining and Marketing - - 4,951 5,688 Corporate and Eliminations - - 1,210 1,068 Consolidated 2,272 2,272 32,770 35,713 (1) Prior to its sale, Marten Hills was reclassified from the Oil Sands segment to the Conventional segment and the comparative period was reclassified.
Schedule of Capital Expenditures	E) Capital Expenditures (1) For the years ended December 31, 2020 2019 2018 Capital Investment (2) Oil Sands 427 656 870 Conventional 78 103 228 Refining and Marketing 276 280 208 Corporate and Eliminations 60 137 57 841 1,176 1,363 Acquisition Capital Oil Sands 6 2 319 Conventional 12 7 22 Refining and Marketing - 4 - Total Capital Expenditures 859 1,189 1,704 (1) Includes expenditures on PP&E and E&E assets. (2 ) Prior to its sale, Marten Hills was reclassified from the Oil Sands segment to the Conventional segment and the comparative periods were reclassified.

General and Administrative (Tab

General and Administrative (Tables)	12 Months Ended
	Dec. 31, 2020
General And Administrative Expenses [Abstract]
Summary of General and Administrative Expenses	For the years ended December 31, 2020 2019 2018 Salaries and Benefits 145 143 205 Administrative and Other 84 95 177 Onerous Contract Provisions (Recovery) 18 (5 ) 629 Stock-Based Compensation Expense (Note 32) 49 67 9 Other Long-Term Incentive Expense (Recovery) (4 ) 31 - 292 331 1,020

Finance Costs (Tables)

Finance Costs (Tables)	12 Months Ended
	Dec. 31, 2020
Finance Costs [Abstract]
Schedule of Finance Cost	For the years ended December 31, 2020 2019 2018 Interest Expense – Short-Term Borrowings and Long-Term Debt 392 407 516 Net (Discount) Premium on Redemption of Long-Term Debt (Note 24) (25 ) (63 ) 17 Interest Expense – Lease Liabilities (Note 25) 87 82 - Unwinding of Discount on Decommissioning Liabilities (Note 27) 57 58 62 Other 25 27 32 536 511 627

Foreign Exchange (Gain) Loss,_2

Foreign Exchange (Gain) Loss, Net (Tables)	12 Months Ended
	Dec. 31, 2020
Foreign Exchange Gains Losses [Abstract]
Schedule of Foreign Exchange Gain Loss Net	For the years ended December 31, 2020 2019 2018 Unrealized Foreign Exchange (Gain) Loss on Translation of: U.S. Dollar Debt Issued From Canada (194 ) (800 ) 602 Other 63 (27 ) 47 Unrealized Foreign Exchange (Gain) Loss (131 ) (827 ) 649 Realized Foreign Exchange (Gain) Loss (50 ) 423 205 (181 ) (404 ) 854

Impairment Charges and Revers_2

Impairment Charges and Reversals (Tables)	12 Months Ended
	Dec. 31, 2020
Disclosure Of Impairment Loss Recognised Or Reversed [Abstract]
Summary of Impairment Losses and Estimated Recoverable Amounts	The following table summarizes the year ended December 31, 2020 impairment losses and estimated recoverable amounts as at December 31, 2020 by CGU: CGU Impairment Amount Recoverable Amount Clearwater 260 160 Elmworth-Wapiti 120 259 Kaybob-Edson 175 384
Summary of Forward Prices Used to Determine Future Cash Flows	The forward prices as at December 31, 2020, used to determine future cash flows from crude oil, NGLs and natural gas reserves were: 2021 2022 2023 2024 2025 Average Annual Increase Thereafter WTI (US$/barrel) (1) 47.17 50.17 53.17 54.97 56.07 2.0 % WCS (C$/barrel) (2) 44.63 48.18 52.10 54.10 55.19 2.0 % Edmonton C5+ (C$/barrel) 59.24 63.19 67.34 69.77 71.18 2.0 % AECO (C$/Mcf) (3) 2.88 2.80 2.71 2.75 2.80 2.0 % (1) West Texas Intermediate (“WTI”). (2) Western Canadian Select (“WCS”). (3) Alberta Energy Company (“AECO”) natural gas. Assumes gas heating value of one million British thermal units per thousand cubic feet (“Mcf”).
Summary of Increase (Decrease) to Recoverable Amount	The sensitivity analysis below shows the impact that a change in the discount rate or forward commodity prices would have had on the calculated recoverable amount in the impairment testing completed as at December 31, 2020 for the following CGUs: Increase (Decrease) to Recoverable Amount One Percent Increase in the Discount Rate One Percent Decrease in the Discount Rate Five Percent Increase in the Forward Price Estimates Five Percent Decrease in the Forward Price Estimates Clearwater (5 ) 6 52 (97 ) Elmworth-Wapiti (7 ) 8 54 (96 ) Kaybob-Edson (13 ) 14 54 (106 ) The sensitivity analysis below shows the impact that a change in the discount rate or forward commodity prices would have had on the calculated recoverable amount in the impairment testing completed as at September 30, 2020 for the following CGU: Increase (Decrease) to Recoverable Amount One Percent Increase in the Discount Rate One Percent Decrease in the Discount Rate Five Percent Increase in the Forward Price Estimates Five Percent Decrease in the Forward Price Estimates Borger (71 ) 81 263 (264 )

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2020
Disclosure Of Income Taxes Continuing Operations [Abstract]
Provision for Income Taxes	The provision for income taxes is: For the years ended December 31, 2020 2019 2018 Current Tax Canada (14 ) 14 (128 ) United States 1 3 2 Total Current Tax Expense (Recovery) (13 ) 17 (126 ) Deferred Tax Expense (Recovery) (838 ) (814 ) (884 ) Tax Expense (Recovery) From Continuing Operations (851 ) (797 ) (1,010 )
Disclosure of Reconciliation of Accounting Profit from Continuing Operations Multiplied by Applicable Tax Rates Explanatory	The following table reconciles income taxes calculated at the Canadian statutory rate with the recorded income taxes: For the years ended December 31, 2020 2019 2018 Earnings (Loss) From Continuing Operations Before Income Tax (3,230 ) 1,397 (3,926 ) Canadian Statutory Rate 24.0% 26.5% 27.0% Expected Income Tax Expense (Recovery) From Continuing Operations (775 ) 370 (1,060 ) Effect on Taxes Resulting From: Statutory and Other Rate Differences 19 (52 ) (57 ) Non-Taxable Capital (Gains) Losses (42 ) (38 ) 89 Non-Recognition of Capital (Gains) Losses (42 ) (39 ) 87 Adjustments Arising From Prior Year Tax Filings (8 ) 4 3 Recognition of U.S. Tax Basis - (387 ) (78 ) Alberta Corporate Rate Reduction (7 ) (671 ) - Other 4 16 6 Total Tax Expense (Recovery) From Continuing Operations (851 ) (797 ) (1,010 ) Effective Tax Rate 26.3% (57.1)% 25.7% The analysis of deferred income tax liabilities and deferred income tax assets is as follows: For the years ended December 31, 2020 2019 Deferred Income Tax Liabilities Deferred Income Tax Liabilities to be Settled Within Twelve Months - 3 Deferred Income Tax Liabilities to be Settled After More Than Twelve Months 4,146 4,540 4,146 4,543 Deferred Income Tax Assets Deferred Income Tax Assets to be Recovered Within Twelve Months (88 ) (113 ) Deferred Income Tax Assets to be Recovered After More Than Twelve Months (860 ) (398 ) (948 ) (511 ) Net Deferred Income Tax Liability 3,198 4,032
Deferred Income Tax Liabilities and Deferred Income Tax Assets	The analysis of deferred income tax liabilities and deferred income tax assets is as follows: For the years ended December 31, 2020 2019 Deferred Income Tax Liabilities Deferred Income Tax Liabilities to be Settled Within Twelve Months - 3 Deferred Income Tax Liabilities to be Settled After More Than Twelve Months 4,146 4,540 4,146 4,543 Deferred Income Tax Assets Deferred Income Tax Assets to be Recovered Within Twelve Months (88 ) (113 ) Deferred Income Tax Assets to be Recovered After More Than Twelve Months (860 ) (398 ) (948 ) (511 ) Net Deferred Income Tax Liability 3,198 4,032
Schedule of Movement in Deferred Income Tax Liabilities and Assets	The movement in deferred income tax liabilities and assets, without taking into consideration the offsetting of balances within the same tax jurisdiction, is: Deferred Income Tax Liabilities PP&E Risk Management Other Total As at December 31, 2018 5,450 44 51 5,545 Charged (Credited) to Earnings (927 ) (43 ) (7 ) (977 ) Charged (Credited) to OCI (25 ) - - (25 ) As at December 31, 2019 4,498 1 44 4,543 Charged (Credited) to Earnings (367 ) (1 ) (22 ) (390 ) Charged (Credited) to OCI (7 ) - - (7 ) As at December 31, 2020 4,124 - 22 4,146 Deferred Income Tax Assets Unused Tax Losses Risk Management Other Total As at December 31, 2018 (357 ) (1 ) (326 ) (684 ) Charged (Credited) to Earnings 129 - 34 163 Charged (Credited) to OCI 3 - 7 10 As at December 31, 2019 (225 ) (1 ) (285 ) (511 ) Charged (Credited) to Earnings (448 ) (12 ) 12 (448 ) Charged (Credited) to OCI 14 - (3 ) 11 As at December 31, 2020 (659 ) (13 ) (276 ) (948 ) Net Deferred Income Tax Liabilities Total Net Deferred Income Tax Liabilities as at December 31, 2018 4,861 Charged (Credited) to Earnings (814 ) Charged (Credited) to OCI (15 ) Net Deferred Income Tax Liabilities as at December 31, 2019 4,032 Charged (Credited) to Earnings (838 ) Charged (Credited) to OCI 4 Net Deferred Income Tax Liabilities as at December 31, 2020 3,198
Schedule of Amounts of Tax Pools Available, Including Tax Losses	The approximate amounts of tax pools available, including tax losses, are: As at December 31, 2020 2019 Canada 6,540 6,113 United States 3,117 2,648 9,657 8,761

Per Share Amounts (Tables)

Per Share Amounts (Tables)	12 Months Ended
	Dec. 31, 2020
Earnings Per Share [Abstract]
Schedule Representing Per Share Amounts	A) Net Earnings (Loss) Per Share – Basic and Diluted For the years ended December 31, 2020 2019 2018 Earnings (Loss) From: Continuing Operations (2,379 ) 2,194 (2,916 ) Discontinued Operations - - 247 Net Earnings (Loss) (2,379 ) 2,194 (2,669 ) Basic – Weighted Average Number of Shares 1,228.9 1,228.8 1,228.8 Dilutive Effect of Cenovus Net Settlement Rights - 0.6 0.4 Diluted – Weighted Average Number of Shares 1,228.9 1,229.4 1,229.2 Basic and Diluted Earnings (Loss) Per Share From: ($) Continuing Operations (1.94 ) 1.78 (2.37 ) Discontinued Operations - - 0.20 (1.94 ) 1.78 (2.17 )

Cash and Cash Equivalents (Tabl

Cash and Cash Equivalents (Tables)	12 Months Ended
	Dec. 31, 2020
Cash And Cash Equivalents [Abstract]
Disclosure Of Cash And Cash Equivalent Explanatory	As at December 31, 2020 2019 Cash 368 108 Short-Term Investments 10 78 378 186

Accounts Receivable and Accru_2

Accounts Receivable and Accrued Revenues (Tables)	12 Months Ended
	Dec. 31, 2020
Trade And Other Current Receivables [Abstract]
Schedule of Accounts Receivable and Accrued Revenues	As at December 31, 2020 2019 Accruals 1,053 1,221 Prepaids and Deposits 121 54 Partner Advances 175 16 Trade 96 212 Joint Operations Receivables 35 36 Other 8 17 1,488 1,556

Inventories (Tables)

Inventories (Tables)	12 Months Ended
	Dec. 31, 2020
Classes Of Inventories [Abstract]
Disclosure Of Detailed Information About Inventories Explanatory	As at December 31, 2020 2019 Product Refining and Marketing 613 874 Oil Sands 382 570 Conventional 1 1 Parts and Supplies 93 87 1,089 1,532

Exploration and Evaluation As_2

Exploration and Evaluation Assets (Tables)	12 Months Ended
	Dec. 31, 2020
Disclosure Of Exploration And Evaluation Assets [Abstract]
Summary of Exploration and Valuation Assets	Total As at December 31, 2018 785 Additions 73 Exploration Expense (Note 10) (82 ) Change in Decommissioning Liabilities 9 Exchange Rate Movements and Other 2 As at December 31, 2019 787 Additions 48 Transfers to PP&E (Note 18) (1) (47 ) Exploration Expense (Note 10) (91 ) Depletion (18 ) Change in Decommissioning Liabilities 5 Divestitures (Note 8) (61 ) As at December 31, 2020 623 (1) Includes the $41 million reclassification of the GORR retained in the sale of the Marten Hills assets (see Note 8).

Property, Plant and Equipment_2

Property, Plant and Equipment, Net (Tables)	12 Months Ended
	Dec. 31, 2020
Disclosure Of Property Plant And Equipment [Abstract]
Summary of Property, Plant and Equipment	Upstream Assets Development & Production Other Upstream Refining Equipment Other (1) Total COST As at December 31, 2018 28,046 333 5,632 1,213 35,224 Adjustment for Change in Accounting Policy (2) - - (4 ) - (4 ) Additions 695 - 228 193 1,116 Change in Decommissioning Liabilities 340 - 9 5 354 Exchange Rate Movements and Other (9 ) - (288 ) 3 (294 ) Divestitures (Note 8) (40 ) - - - (40 ) As at December 31, 2019 29,032 333 5,577 1,414 36,356 Additions 475 - 243 93 811 Transfers From E&E Assets (Note 17) 6 41 - - 47 Change in Decommissioning Liabilities (11 ) - 3 2 (6 ) Exchange Rate Movements and Other (6 ) - (152 ) (1 ) (159 ) Divestitures (3 ) - - - (3 ) As at December 31, 2020 29,493 374 5,671 1,508 37,046 ACCUMULATED DEPRECIATION, DEPLETION AND AMORTIZATION As at December 31, 2018 3,918 333 1,442 833 6,526 Adjustment for Change in Accounting Policy (2) - - (1 ) - (1 ) Depreciation, Depletion and Amortization 1,735 - 241 75 2,051 Impairment Charges (Note 10) 20 - - 10 30 Exchange Rate Movements and Other 31 - (86 ) - (55 ) Divestitures (Note 8) (29 ) - - - (29 ) As at December 31, 2019 5,675 333 1,596 918 8,522 Depreciation, Depletion and Amortization 1,768 - 242 109 2,119 Impairment Charges (Note 10) 607 - 450 52 1,109 Exchange Rate Movements and Other (22 ) - (93 ) - (115 ) As at December 31, 2020 8,028 333 2,195 1,079 11,635 CARRYING VALUE As at December 31, 2018 24,128 - 4,190 380 28,698 As at December 31, 2019 23,357 - 3,981 496 27,834 As at December 31, 2020 21,465 41 3,476 429 25,411 (1) Primarily consists of crude-by-rail terminal, office furniture, fixtures, leasehold improvements, information technology and aircraft. (2) Effective January 1, 2019, the Company adopted IFRS 16.
Summary of PP&E Under Construction and Not Subject to DD&A	PP&E includes the following amounts in respect of assets under construction and not subject to DD&A: As at December 31, 2020 2019 Development and Production 1,807 1,836 Refining Equipment 226 172 2,033 2,008

Right of Use Assets, Net (Table

Right of Use Assets, Net (Tables)	12 Months Ended
	Dec. 31, 2020
Disclosure Of Quantitative Information About Rightofuse Assets [Abstract]
Summary of Right of Use Assets, Net	Real Estate Railcars & Barges Storage Assets (1) Refining Equipment Other Total COST As at January 1, 2019 (2) 517 63 292 13 9 894 Additions 10 436 172 - 6 624 Terminations - - (11 ) - - (11 ) Reclassifications (8 ) - - - - (8 ) Re-measurement - (2 ) 18 (2 ) - 14 Exchange Rate Movements and Other (10 ) (2 ) (7 ) (1 ) (1 ) (21 ) As at December 31, 2019 509 495 464 10 14 1,492 Additions 1 18 22 5 7 53 Terminations - - (1 ) - - (1 ) Modifications - - 1 - (3 ) (2 ) Reclassifications (14 ) - - - - (14 ) Re-measurement - (20 ) 19 - (1 ) (2 ) Exchange Rate Movements and Other (1 ) (13 ) (8 ) - (2 ) (24 ) As at December 31, 2020 495 480 497 15 15 1,502 ACCUMULATED DEPRECIATION As at January 1, 2019 (2) - - - 1 - 1 Depreciation 29 55 75 2 4 165 Impairment Charges (Note 10) 3 - - - - 3 Terminations - - (1 ) - - (1 ) Exchange Rate Movements and Other - - (1 ) - - (1 ) As at December 31, 2019 32 55 73 3 4 167 Depreciation 27 86 95 2 5 215 Impairment Charges (Note 10) - 3 - - - 3 Terminations - - (1 ) - - (1 ) Exchange Rate Movements and Other (1 ) (13 ) (5 ) - (2 ) (21 ) As at December 31, 2020 58 131 162 5 7 363 CARRYING VALUE As at January 1, 2019 (2) 517 63 292 12 9 893 As at December 31, 2019 477 440 391 7 10 1,325 As at December 31, 2020 437 349 335 10 8 1,139 (1) Includes caverns and tanks. (2) Effective January 1, 2019, the Company adopted IFRS 16.

Other Assets (Tables)

Other Assets (Tables)	12 Months Ended
	Dec. 31, 2020
Other Noncurrent Assets [Abstract]
Summary of Other Assets	As at December 31, 2020 2019 Intangible Assets 89 101 Equity Investments (Note 35A) 52 52 Investment in Associate (Note 8) 97 - Net Investment in Finance Leases 52 30 Long-Term Receivables and Prepaids 11 28 Other 12 - 313 211

Accounts Payable and Accrued _2

Accounts Payable and Accrued Liabilities (Tables)	12 Months Ended
	Dec. 31, 2020
Trade And Other Current Payables [Abstract]
Schedule of Accounts Payable and Accrued Liabilities	As at December 31, 2020 2019 Accruals 912 1,085 Trade 608 954 Interest 77 49 Partner Advances 175 16 Employee Long-Term Incentives 130 60 Joint Operations Payable 6 2 Risk Management 58 2 Onerous Contract Provisions 26 17 Other 26 44 2,018 2,229

Long-term Debt and Capital St_2

Long-term Debt and Capital Structure (Tables)	12 Months Ended
	Dec. 31, 2020
Borrowings [Abstract]
Schedule of Long Term Debt	As at December 31, Notes 2020 2019 Revolving Term Debt (1) A - 265 U.S. Dollar Denominated Unsecured Notes B 7,510 6,492 Total Debt Principal 7,510 6,757 Debt Discounts and Transaction Costs (69 ) (58 ) Long-Term Debt 7,441 6,699 (1) Revolving term debt may include Bankers’ Acceptances, London Interbank Offered Rate based loans, prime rate loans and U.S. base rate loans.
Schedule Remaining Principal Amounts of U.S. Dollar Denominated Unsecured Notes	The remaining principal amounts of the Company’s U.S. dollar denominated unsecured notes are: 2020 2019 As at December 31, US$ Principal Amount Total C$ Equivalent US$ Principal Amount Total C$ Equivalent 3.00% due August 15, 2022 500 637 500 650 3.80% due September 15, 2023 450 573 450 585 5.38% due July 15, 2025 1,000 1,273 - - 4.25% due April 15, 2027 962 1,225 962 1,249 5.25% due June 15, 2037 583 742 641 833 6.75% due November 15, 2039 1,390 1,770 1,400 1,818 4.45% due September 15, 2042 155 198 155 202 5.20% due September 15, 2043 58 74 58 75 5.40% due June 15, 2047 800 1,018 832 1,080 5,898 7,510 4,998 6,492
Schedule of Mandatory Debt Payments	As at December 31, 2020 US$ Principal Amount Total C$ Equivalent 2022 500 637 2023 450 573 2025 1,000 1,273 Thereafter 3,948 5,027 5,898 7,510
Summary of Net Debt to Adjusted EBITDA	Net Debt to Adjusted EBITDA (1) As at December 31, 2020 2019 2018 Short-Term Borrowings 121 - - Current Portion of Long-Term Debt - - 682 Long-Term Debt 7,441 6,699 8,482 Less: Cash and Cash Equivalents (378 ) (186 ) (781 ) Net Debt 7,184 6,513 8,383 Net Earnings (Loss) (2,379 ) 2,194 (2,669 ) Add (Deduct): Finance Costs 536 511 628 Interest Income (9 ) (12 ) (19 ) Income Tax Expense (Recovery) (851 ) (797 ) (920 ) Depreciation, Depletion and Amortization 3,464 2,249 2,131 Exploration Expense 91 82 2,123 Unrealized (Gain) Loss on Risk Management 56 149 (1,249 ) Foreign Exchange (Gain) Loss, Net (181 ) (404 ) 854 Re-measurement of Contingent Payment (80 ) 164 50 (Gain) Loss on Discontinuance - - (301 ) (Gain) Loss on Divestitures of Assets (81 ) (2 ) 795 Other (Income) Loss, Net 40 9 13 Adjusted EBITDA 606 4,143 1,436 Net Debt to Adjusted EBITDA 11.9x 1.6x 5.8x (1) IFRS 16 was adopted January 1, 2019 using the modified retrospective approach; therefore, comparative information has not been restated.
Summary of Net Debt to Capitalization	Net Debt to Capitalization As at December 31, 2020 2019 2018 Net Debt 7,184 6,513 8,383 Shareholders’ Equity 16,707 19,201 17,468 23,891 25,714 25,851 Net Debt to Capitalization 30% 25% 32%

Lease Liabilities (Tables)

Lease Liabilities (Tables)	12 Months Ended
	Dec. 31, 2020
Lease Liabilities [Abstract]
Summary of Lease Liabilities	2020 2019 Lease Liabilities, Beginning of Year 1,916 1,494 Additions 49 590 Interest Expense (Note 6) 87 82 Lease Payments (284 ) (232 ) Terminations (1 ) (11 ) Modifications (2 ) - Re-measurement (2 ) 15 Exchange Rate Movements and Other (6 ) (22 ) Lease Liabilities, End of Year 1,757 1,916 Less: Current Portion 184 196 Long-Term Portion 1,573 1,720
Summary of Lease Liabilities Depending on Duration of Lease Term	For the years ended December 31, 2020 2019 Variable Lease Payments 16 19 Short-Term Lease Payments 6 13

Contingent Payment (Tables)

Contingent Payment (Tables)	12 Months Ended
	Dec. 31, 2020
Disclosure Of Contingent Liabilities In Business Combination [Abstract]
Summary of Contingent Payment	2020 2019 Contingent Payment, Beginning of Year 143 132 Re-measurement (1) (80 ) 164 Liabilities Settled or Payable - (153 ) Contingent Payment, End of Year 63 143 Less: Current Portion 36 79 Long-Term Portion 27 64 (1) Contingent payment is carried at fair value. Changes in fair value are recorded in net earnings.

Decommissioning Liabilities (Ta

Decommissioning Liabilities (Tables)	12 Months Ended
	Dec. 31, 2020
Provision For Decommissioning Restoration And Rehabilitation Costs [Abstract]
Summary of Decommissioning Provision	The aggregate carrying amount of the obligation is: 2020 2019 Decommissioning Liabilities, Beginning of Year 1,235 875 Liabilities Incurred 14 3 Liabilities Settled (42 ) (52 ) Liabilities Disposed (2 ) (8 ) Change in Estimated Future Cash Flows 13 21 Change in Discount Rate (28 ) 339 Unwinding of Discount on Decommissioning Liabilities (Note 6) 57 58 Foreign Currency Translation 1 (1 ) Decommissioning Liabilities, End of Year 1,248 1,235
Summary of Changes to the Credit-Adjusted Risk-Free Rate or the Inflation Rate Impact on the Decommissioning Liabilities	Changes to the credit-adjusted risk-free rate or the inflation rate would have the following impact on the decommissioning liabilities: 2020 2019 As at December 31, Sensitivity Range Increase Decrease Increase Decrease Credit-Adjusted Risk-Free Rate ± one percent (228 ) 313 (236 ) 332 Inflation Rate ± one percent 321 (235 ) 340 (243 )

Other Liabilities (Tables)

Other Liabilities (Tables)	12 Months Ended
	Dec. 31, 2020
Disclosure Of Other Non Current Liabilities [Abstract]
Summary of Other Liabilities	As at December 31, 2020 2019 Employee Long-Term Incentives 33 103 Pension and Other Post-Employment Benefit Plan (Note 29) 91 73 Onerous Contract Provisions 39 46 Other 18 19 181 241

Pensions and Other Post-Emplo_2

Pensions and Other Post-Employment Benefits (Tables)	12 Months Ended
	Dec. 31, 2020
Pensions And Other Post Employment Benefits [Abstract]
Summary of Defined Benefit and OPEB Plan Obligation and Funded Status	A) Defined Benefit and OPEB Plan Obligation and Funded Status Information related to defined benefit pension and OPEB plans, based on actuarial estimations, is: Pension Benefits OPEB As at December 31, 2020 2019 2020 2019 Defined Benefit Obligation Defined Benefit Obligation, Beginning of Year 158 167 22 21 Current Service Costs 13 11 1 1 Interest Costs (1) 5 6 - 1 Benefits Paid (6 ) (36 ) (2 ) (2 ) Plan Participant Contributions 2 2 - - Re-measurements: (Gains) Losses From Experience Adjustments 1 (4 ) (2 ) - (Gains) Losses From Changes in Financial Assumptions 15 12 1 1 Defined Benefit Obligation, End of Year 188 158 20 22 Plan Assets Fair Value of Plan Assets, Beginning of Year 107 113 - - Employer Contributions 6 9 - - Plan Participant Contributions 2 2 - - Benefits Paid (5 ) (35 ) - - Interest Income (1) 2 3 - - Re-measurements: Return on Plan Assets (Excluding Interest Income) 5 15 - - Fair Value of Plan Assets, End of Year 117 107 - - Pension and OPEB (Liability) (2) (71 ) (51 ) (20 ) (22 ) (1) Based on the discount rate of the defined benefit obligation at the beginning of the year. (2) Pension and OPEB liabilities are included in other liabilities on the Consolidated Balance Sheets.
Summary of Pension and OPEB Costs	B) Pension and OPEB Costs Pension Benefits OPEB For the years ended December 31, 2020 2019 2018 2020 2019 2018 Defined Benefit Plan Cost Current Service Costs 13 11 13 1 1 1 Past Service Costs – Curtailments - - (2 ) - - - Net Interest Costs 3 3 3 - 1 1 Re-measurements: Return on Plan Assets (Excluding Interest Income) (5 ) (15 ) 7 - - - (Gains) Losses From Experience Adjustments 1 (4 ) - (2 ) - - (Gains) Losses From Changes in Financial Assumptions 15 12 - 1 1 (1 ) Defined Benefit Plan Cost (Recovery) 27 7 21 - 3 1 Defined Contribution Plan Cost 22 21 22 - - - Total Plan Cost 49 28 43 - 3 1
Summary of Fair Value of the Plan Assets	The fair value of the plan assets is: As at December 31, 2020 2019 Equity Funds 58 59 Fixed Income Funds 35 35 Real Estate Funds 6 - Listed Infrastructure Funds 8 9 Emerging Market Debt Funds 7 - Non-Invested Assets 1 2 Cash and Cash Equivalents 2 2 117 107
Summary of principal weighted average actuarial assumptions used to determine benefit obligations and expenses	The principal weighted average actuarial assumptions used to determine benefit obligations and expenses are as follows: Pension Benefits OPEB For the years ended December 31, 2020 2019 2018 2020 2019 2018 Discount Rate 2.50 % 3.00 % 3.50 % 2.50 % 3.00 % 3.50 % Future Salary Growth Rate 3.97 % 3.94 % 3.88 % 4.94 % 5.08 % 5.08 % Average Longevity (years) 88.3 88.2 88.2 88.2 88.2 88.1 Health Care Cost Trend Rate N/A N/A N/A 6.00 % 6.00 % 6.00 %
Sensitivity of defined benefit and OPEB obligation to changes in relevant actuarial assumptions	The sensitivity of the defined benefit and OPEB obligation to changes in relevant actuarial assumptions is: 2020 2019 As at December 31, Increase Decrease Increase Decrease One Percent Change: Discount Rate (31 ) 40 (25 ) 32 Future Salary Growth Rate 4 (4 ) 3 (3 ) Health Care Cost Trend Rate 1 (1 ) 1 (1 ) One Year Change in Assumed Life Expectancy 4 (4 ) 3 (3 )

Share Capital (Tables)

Share Capital (Tables)	12 Months Ended
	Dec. 31, 2020
Disclosure Of Classes Of Share Capital [Abstract]
Summary of Share Capital	B) Issued and Outstanding 2020 2019 As at December 31, Number of Common Shares (thousands) Amount Number of Common Shares (thousands) Amount Outstanding, Beginning of Year 1,228,828 11,040 1,228,790 11,040 Common Shares Issued Under Stock Option Plan (Note 32) 42 - 38 - Outstanding, End of Year 1,228,870 11,040 1,228,828 11,040
Disclosure Of Paid In Surplus Includes Stock Based Compensation Expense Explanatory	Cenovus’s paid in surplus reflects the Company’s retained earnings prior to the split of Encana Corporation (“Encana”) under the plan of arrangement into two independent energy companies, Encana (now known as Ovintiv Inc.) and Cenovus (pre-arrangement earnings). In addition, paid in surplus includes stock-based compensation expense related to the Company’s NSRs discussed in Note 32A. Pre-Arrangement Earnings Stock-Based Compensation Total As at December 31, 2018 4,086 281 4,367 Stock-Based Compensation Expense - 10 10 As at December 31, 2019 4,086 291 4,377 Stock-Based Compensation Expense - 14 14 As at December 31, 2020 4,086 305 4,391

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Income (Loss) (Tables)	12 Months Ended
	Dec. 31, 2020
Disclosure Of Accumulated Other Comprehensive Income Loss [Abstract]
Summary of Accumulated Other Comprehensive Income (Loss)	Defined Benefit Pension Plan Private Equity Instruments Foreign Currency Translation Adjustment Total As at December 31, 2018 (7 ) 15 1,030 1,038 Other Comprehensive Income (Loss), Before Tax 6 14 (228 ) (208 ) Income Tax (1 ) (2 ) - (3 ) As at December 31, 2019 (2 ) 27 802 827 Other Comprehensive Income (Loss), Before Tax (10 ) - (44 ) (54 ) Income Tax 2 - - 2 As at December 31, 2020 (10 ) 27 758 775

Stock-Based Compensation Plans

Stock-Based Compensation Plans (Tables)	12 Months Ended
	Dec. 31, 2020
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Summary of Stock-Based Compensation	E) Total Stock-Based Compensation For the years ended December 31, 2020 2019 2018 Net Settlement Rights 11 9 6 Performance Share Units 19 15 (6 ) Restricted Share Units 23 34 9 Deferred Share Units (4 ) 9 - Stock-Based Compensation Expense 49 67 9 Stock-Based Compensation Costs Capitalized 16 20 4 65 87 13
NSRs [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Summary of Assumptions Used to Determine Fair Value of Options Granted	The fair value of each NSR was estimated on its grant date using the Black-Scholes-Merton valuation model with weighted average assumptions as follows: Risk-Free Interest Rate 1.19 % Expected Dividend Yield 1.77 % Expected Volatility (1) 29.74 % Expected Life (years) 5.00 (1) Expected volatility has been based on historical share volatility of the Company and comparable industry peers.
Summary of Units Activity and Related Information	The following tables summarize information related to the NSRs: For the year ended December 31, 2020 Number of NSRs (thousands) Weighted Average Exercise Price ($) Outstanding, Beginning of Year 31,528 22.61 Granted 5,783 11.73 Exercised (42 ) 9.48 Forfeited (416 ) 23.52 Expired (6,256 ) 32.60 Outstanding, End of Year 30,597 18.52
Summary of Options Outstanding and Exercisable by Range of Exercise Price	Outstanding NSRs Exercisable NSRs As at December 31, 2020 Range of Exercise Price ($) Number of NSRs (thousands) Weighted Average Remaining Contractual Life (years) Weighted Average Exercise Price ($) Number of NSRs (thousands) Weighted Average Exercise Price ($) 5.00 to 9.99 2,796 4.2 9.48 1,596 9.48 10.00 to 14.99 12,921 5.2 12.27 4,189 13.53 15.00 to 19.99 2,691 2.3 19.47 2,691 19.47 20.00 to 24.99 3,078 1.1 22.26 3,078 22.26 25.00 to 29.99 8,540 0.1 28.37 8,540 28.37 30.00 to 34.99 571 0.5 32.27 571 32.27 30,597 2.9 18.52 20,665 21.94
PSUs [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Summary of Units Activity and Related Information	The following table summarizes the information related to the PSUs held by Cenovus employees: For the year ended December 31, 2020 Number of PSUs (thousands) Outstanding, Beginning of Year 6,912 Granted 3,846 Vested and Paid Out (1,223 ) Cancelled (449 ) Units in Lieu of Dividends 198 Outstanding, End of Year 9,284
RSUs [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Summary of Units Activity and Related Information	The following table summarizes the information related to the RSUs held by Cenovus employees: For the year ended December 31, 2020 Number of RSUs (thousands) Outstanding, Beginning of Year 8,372 Granted 2,686 Vested and Paid Out (2,606 ) Cancelled (234 ) Units in Lieu of Dividends 212 Outstanding, End of Year 8,430
DSUs [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Summary of Units Activity and Related Information	The following table summarizes the information related to the DSUs held by Cenovus directors, officers and employees: For the year ended December 31, 2020 Number of DSUs (thousands) Outstanding, Beginning of Year 1,237 Granted to Directors 288 Granted 30 Units in Lieu of Dividends 33 Redeemed (255 ) Outstanding, End of Year 1,333

Employee Salaries and Benefit_2

Employee Salaries and Benefit Expenses (Tables)	12 Months Ended
	Dec. 31, 2020
Disclosure Of Salaries And Employee Benefits [Abstract]
Summary of Employee Salaries and Benefit Expenses	For the years ended December 31, 2020 2019 2018 Salaries, Bonuses and Other Short-Term Employee Benefits 605 567 580 Post-Employment Benefits 33 29 30 Stock-Based Compensation Expense (Note 32) 49 67 9 Other Long-Term Incentive Benefits (4 ) 31 - Termination Benefits 9 6 63 692 700 682 Stock-based compensation includes the costs recorded during the year associated with NSRs, PSUs, RSUs and DSUs.

Related Party Transactions (Tab

Related Party Transactions (Tables)	12 Months Ended
	Dec. 31, 2020
Key Management Personnel of Entity or Parent [Member]
Disclosure Of Transactions Between Related Parties [Line Items]
Summary of Key Management Compensation	Key management includes Directors (executive and non-executive), Executive Officers, Senior Vice-Presidents and Vice-Presidents. The compensation paid or payable to key management is: For the years ended December 31, 2020 2019 2018 Salaries, Director Fees and Short-Term Benefits 21 24 20 Post-Employment Benefits 3 2 3 Stock-Based Compensation 15 22 5 Other Long-Term Incentive Benefits 1 1 - Termination Benefits 6 - 9 46 49 37

Financial Instruments (Tables)

Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2020
Disclosure Of Financial Instruments [Abstract]
Reconciliation of Changes in the Fair Value of Available for Sale Financial Assets	The following table provides a reconciliation of changes in the fair value of private equity investments classified at FVOCI: 2020 2019 Fair Value, Beginning of Year 52 38 Change in Fair Value (1) - 14 Fair Value, End of Year 52 52 (1) Changes in fair value are recorded in OCI.
Summary of Unrealized Risk Management Positions	Summary of Unrealized Risk Management Positions 2020 2019 Risk Management Risk Management As at December 31, Asset Liability Net Asset Liability Net Crude Oil, Natural Gas and Condensate 5 58 (53 ) 5 2 3
Summary of Fair Value Hierarchy for Risk Management Assets and Liabilities Carried at Fair Value	The following table presents the Company’s fair value hierarchy for risk management assets and liabilities carried at fair value: As at December 31, 2020 2019 Level 2 – Prices Sourced From Observable Data or Market Corroboration (53 ) 3
Summary of Changes in the Fair Value of Cenovus's Risk Management Assets and Liabilities	The following table summarizes the changes in the fair value of Cenovus’s risk management assets and liabilities: 2020 2019 Fair Value of Contracts, Beginning of Year 3 160 Fair Value of Contracts Realized During the Year 252 7 Change in Fair Value of Contracts in Place at Beginning of Year and Contracts Entered Into During the Year (308 ) (156 ) Unrealized Foreign Exchange Gain (Loss) on U.S. Dollar Contracts - (8 ) Fair Value of Contracts, End of Year (53 ) 3
Summary of Offsetting Risk Management Positions	The following table provides a summary of the Company’s offsetting risk management positions: 2020 2019 Risk Management Risk Management As at December 31, Asset Liability Net Asset Liability Net Recognized Risk Management Positions Gross Amount 70 123 (53 ) 13 10 3 Amount Offset (65 ) (65 ) - (8 ) (8 ) - Net Amount per Consolidated Financial Statements 5 58 (53 ) 5 2 3
Summary of Changes in Inputs to Option Pricing Model, Resulted in Unrealized Gains (Losses) Impacting Earnings Before Income Tax	Changes in the following inputs to the option pricing model, with fluctuations in all other variables held constant, could have resulted in an unrealized gain (loss) impacting earnings before income tax as follows: As at December 31, 2020 Sensitivity Range Increase Decrease WCS Forward Prices ± $5.00 per barrel (41 ) 32 WTI Option Volatility ± five percent (18 ) 17 Canadian to U.S. Dollar Foreign Exchange Rate Option Volatility ± five percent 7 (10 ) As at December 31, 2019 Sensitivity Range Increase Decrease WCS Forward Prices ± $5.00 per barrel (129 ) 80 WTI Option Volatility ± five percent (45 ) 42 Canadian to U.S. Dollar Foreign Exchange Rate Option Volatility ± five percent 10 (19 )
Summary of Earnings Impact of (Gains) Losses from Risk Management Positions	Earnings Impact of (Gains) Losses From Risk Management Positions For the years ended December 31, 2020 2019 2018 Realized (Gain) Loss (1) 252 7 1,554 Unrealized (Gain) Loss (2) 56 149 (1,249 ) (Gain) Loss on Risk Management From Continuing Operations 308 156 305 ( 1 ) Realized gains and losses on risk management are recorded in the reportable segment to which the derivative instrument relates. ( 2 ) Unrealized gains and losses on risk management are recorded in the Corporate and Eliminations segment.

Risk Management (Tables)

Risk Management (Tables)	12 Months Ended
	Dec. 31, 2020
Risk Management [Abstract]
Net Fair Value of Risk Management Positions	Net Fair Value of Risk Management Positions As at December 31, 2020 Notional Volumes (1) (2) Terms (3) Weighted Average Price (1) (2) Fair Value Asset (Liability) Crude Oil and Condensate Contracts WTI Fixed - Sell 19.6 MMbbls January 2021 - June 2022 US$43.99/bbl (113 ) WTI Fixed - Buy 11.7 MMbbls February 2021 - June 2022 US$44.55/bbl 59 Other Financial Positions (4) 1 Total Fair Value (53 ) (1) Million barrels (“MMbbls”). Barrel (“bbl”). (2) Notional volumes and weighted average price represent various contracts over the respective terms. The notional volumes and weighted average price may fluctuate from month to month as it represents the averages for various individual contracts with different terms. (3) Contract terms represents averages for various individual contracts with different terms and range from one to twenty-three months. (4) Other financial positions consist of risk management positions related to WCS and condensate differential contracts, Belvieu and natural gas fixed contracts and the Company’s Refining and Marketing segment.
Disclosure of Derivative Financial Instruments [Line Items]
Summary of Changes in Inputs to Option Pricing Model, Resulted in Unrealized Gains (Losses) Impacting Earnings Before Income Tax	Changes in the following inputs to the option pricing model, with fluctuations in all other variables held constant, could have resulted in an unrealized gain (loss) impacting earnings before income tax as follows: As at December 31, 2020 Sensitivity Range Increase Decrease WCS Forward Prices ± $5.00 per barrel (41 ) 32 WTI Option Volatility ± five percent (18 ) 17 Canadian to U.S. Dollar Foreign Exchange Rate Option Volatility ± five percent 7 (10 ) As at December 31, 2019 Sensitivity Range Increase Decrease WCS Forward Prices ± $5.00 per barrel (129 ) 80 WTI Option Volatility ± five percent (45 ) 42 Canadian to U.S. Dollar Foreign Exchange Rate Option Volatility ± five percent 10 (19 )
Undiscounted Cash Outflows Relating to Financial Liabilities	Undiscounted cash outflows relating to financial liabilities are: As at December 31, 2020 Less than 1 Year Years 2 and 3 Years 4 and 5 Thereafter Total Accounts Payable and Accrued Liabilities 2,018 - - - 2,018 Short-Term Borrowings (1) 121 - - - 121 Long-Term Debt (1) 385 1,965 1,966 8,627 12,943 Contingent Payment (2) 36 28 - - 64 Lease Liabilities (1) 254 445 365 1,412 2,476 As at December 31, 2019 Less than 1 Year Years 2 and 3 Years 4 and 5 Thereafter Total Accounts Payable and Accrued Liabilities 2,229 - - - 2,229 Long-Term Debt (1) 344 1,338 1,465 9,326 12,473 Contingent Payment (2) 79 69 - - 148 Lease Liabilities (1) 277 466 410 1,544 2,697 ( 1 ) Principal and interest, including current portion. ( 2 ) Refer to Note 35C for fair value assumptions .
Commodity Price Risk [Member]
Disclosure of Derivative Financial Instruments [Line Items]
Summary of Changes in Inputs to Option Pricing Model, Resulted in Unrealized Gains (Losses) Impacting Earnings Before Income Tax	The following table summarizes the sensitivity of the fair value of Cenovus’s risk management positions to independent fluctuations in commodity prices, with all other variables held constant. Management believes the fluctuations identified in the table below are a reasonable measure of volatility. The impact of fluctuating commodity prices on the Company’s open risk management positions could have resulted in unrealized gains (losses) impacting earnings before income tax as follows: As at December 31, 2020 Sensitivity Range Increase Decrease Crude Oil Commodity Price ± US$5.00 per bbl Applied to WTI and Condensate Hedges (44 ) 44 Crude Oil Differential Price ± US$2.50 per bbl Applied to Differential Hedges Tied to Production (2 ) 2 As at December 31, 2019 Sensitivity Range Increase Decrease Crude Oil Commodity Price ± US$5.00 per bbl Applied to WTI and Condensate Hedges 3 (3 ) Crude Oil Differential Price ± US$2.50 per bbl Applied to Differential Hedges Tied to Production 5 (5 )
Currency risk [Member]
Disclosure of Derivative Financial Instruments [Line Items]
Summary of Changes in Inputs to Option Pricing Model, Resulted in Unrealized Gains (Losses) Impacting Earnings Before Income Tax	In respect of these financial instruments, the impact of changes in the Canadian per U.S. dollar exchange rate would have resulted in a change to the foreign exchange (gain) loss as follows: For the years ended December 31, 2020 2019 $0.05 Increase in the Canadian per U.S. Dollar Foreign Exchange Rate 300 250 $0.05 Decrease in the Canadian per U.S. Dollar Foreign Exchange Rate (300 ) (250 )

Supplementary Cash Flow Infor_2

Supplementary Cash Flow Information (Tables)	12 Months Ended
	Dec. 31, 2020
Disclosure Of Supplementary Cash Flow Information [Abstract]
Summary of Supplementary Cash Flow Information	For the years ended December 31, 2020 2019 2018 Interest Paid 381 457 564 Interest Received 5 12 19 Income Taxes Paid 18 17 116
Summary of Reconciliation of Cash Flows from Financing Activities	The following table provides a reconciliation of cash flows arising from financing activities: Dividends Payable Short-Term Borrowings Long-Term Debt Lease Liabilities As at December 31, 2017 - - 9,513 - Changes From Financing Cash Flows: Repayment of Long-Term Debt - - (1,144 ) - Net Issuance (Repayment) of Revolving Long-Term Debt - - (20 ) - Dividends Paid (245 ) - - - Non-Cash Changes: Dividends Declared 245 - - - Foreign Exchange (Gain) Loss - - 817 - Finance Costs - - (2 ) - As at December 31, 2018 - - 9,164 - Adjustment for Change in Accounting Policy (1) - - - 1,494 Changes From Financing Cash Flows: Dividends Paid (260 ) - - - Repayment of Long-Term Debt - - (2,279 ) - Net Issuance (Repayment) of Revolving Long-Term Debt - - 276 - Principal Repayment of Leases - - - (150 ) Non-Cash Changes: Dividends Declared 260 - - - Foreign Exchange (Gain) Loss - - (399 ) (23 ) Gain on Repurchase of Debt and Amortization of Debt Issuance Costs - - (63 ) - Lease Additions - - - 590 Re-measurement of Lease Liabilities - - - 15 Lease Terminations - - - (11 ) Other - - - 1 As at December 31, 2019 - - 6,699 1,916 Changes From Financing Cash Flows: Dividends Paid (77 ) - - - Issuance (Repayment) of Short-Term Borrowings - 117 - - Issuance of Long-Term Debt - - 1,326 - Repayment of Long-Term Debt - - (112 ) - Net Issuance (Repayment) of Revolving Long-Term Debt - - (220 ) - Principal Repayment of Leases - - - (197 ) Non-Cash Changes: Dividends Declared 77 - - - Foreign Exchange (Gain) Loss - 4 (231 ) (6 ) Gain on Repurchase of Debt and Amortization of Debt Issuance Costs - - (20 ) - Lease Additions - - - 49 Lease Terminations - - - (1 ) Lease Modifications - - - (2 ) Re-measurement of Lease Liabilities - - - (2 ) Other - - (1 ) - As at December 31, 2020 - 121 7,441 1,757 (1) Effective January 1, 2019, the Company adopted IFRS 16.

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2020
Commitments And Contingencies [Abstract]
Summary of Future Payments of Commitments	These items exclude amounts recorded in the Consolidated Balance Sheets. As at December 31, 2020 1 Year 2 Years 3 Years 4 Years 5 Years Thereafter Total Transportation and Storage (1) 1,014 954 1,341 1,444 1,107 15,537 21,397 Real Estate (2) 34 36 38 41 44 604 797 Capital Commitments 1 2 - - - - 3 Other Long-Term Commitments 104 45 32 32 24 85 322 Total Payments (3) 1,153 1,037 1,411 1,517 1,175 16,226 22,519 As at December 31, 2019 1 Year 2 Years 3 Years 4 Years 5 Years Thereafter Total Transportation and Storage (1) 1,005 959 1,026 1,456 1,381 15,672 21,499 Real Estate (2) 35 36 38 39 42 662 852 Other Long-Term Commitments 104 44 36 34 28 108 354 Total Payments (3) 1,144 1,039 1,100 1,529 1,451 16,442 22,705 (1) Includes transportation commitments of $ 14 (2) Relates to the non-lease components of lease liabilities consisting of operating costs and unreserved parking for office space. Excludes committed payments for which a provision has been provided. ( 3 ) Contracts undertaken on behalf of WRB are reflected at Cenovus’s 50 percent interest.

Subsequent Event (Tables)

Subsequent Event (Tables)	12 Months Ended
	Dec. 31, 2020
Disclosure Of Nonadjusting Events After Reporting Period [Abstract]
Business Combination Subsequent to Year End and Before Report Issuance	The following table summarizes the details of the consideration and the recognized amounts of assets acquired and liabilities assumed at the date of the acquisition. As at January 1, 2021 Consideration Common Shares 6,111 Preferred Shares 519 Share Purchase Warrants 216 Replacement Stock Options 9 Non-Controlling Interest 11 Total Consideration and Non-Controlling Interest 6,866 Identifiable Assets Acquired and Liabilities Assumed Cash 735 Restricted Cash 164 Accounts Receivable and Accrued Revenues 1,272 Inventories 1,118 Property, Plant and Equipment, Intangible Assets and Deferred Income Tax Assets 15,227 Right-of-Use Assets 1,137 Long-Term Income Tax Receivable 202 Other Assets 200 Investments in Joint Ventures 457 Accounts Payable and Accrued Liabilities (2,224 ) Income Tax Payable (59 ) Current Portion of Long-Term Debt (40 ) Long-Term Debt (6,602 ) Lease Liabilities (1,447 ) Decommissioning Liabilities (2,835 ) Other Liabilities (439 ) Total Identifiable Net Assets 6,866

Description of Business and S_3

Description of Business and Segmented Disclosures - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2020CAD ($)RefineryCustomer	Dec. 31, 2019CAD ($)Customer	Dec. 31, 2018CAD ($)Customer
Disclosure Of Operating Segments [Line Items]
Number of major customers | Customer	3	2	3
Gross Sales	$ 13,591	$ 21,353	$ 21,389
Customer One [Member]
Disclosure Of Operating Segments [Line Items]
Gross Sales	4,323	6,922	7,840
Customer Two [Member]
Disclosure Of Operating Segments [Line Items]
Gross Sales	1,834	$ 2,316	2,285
Customer Three [Member]
Disclosure Of Operating Segments [Line Items]
Gross Sales	$ 1,472		$ 2,263
Bottom of Range [Member]
Disclosure Of Operating Segments [Line Items]
Percentage of entity's revenue from gross sales	10.00%	10.00%	10.00%
Canada [Member]
Disclosure Of Operating Segments [Line Items]
Sales of crude oil, natural gas and NGLs	$ 2,639	$ 4,002	$ 2,500
Refining and Marketing [Member]
Disclosure Of Operating Segments [Line Items]
Number of refineries | Refinery	2
Gross Sales	$ 6,051	$ 10,513	$ 11,183

Description of Business and S_4

Description of Business and Segmented Disclosures - Schedule of Segment and Operational Information (Detail) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenues
Gross Sales	$ 13,591	$ 21,353	$ 21,389
Less: Royalties	364	1,173	546
Revenue	13,227	20,180	20,843
Expenses
Purchased Product	5,119	8,378	8,684
Transportation and Blending	4,444	5,184	5,942
Operating	1,930	2,088	2,184
Inventory Write-Down (Reversal)	555	49	60
(Gain) Loss on Risk Management	308	156	305
Depreciation, Depletion and Amortization	3,464	2,249	2,131
Exploration Expense	91	82	2,123
Segment Income (Loss)	(2,684)	1,994	(586)
General and Administrative	292	331	1,020
Finance Costs	536	511	627
Interest Income	(9)	(12)	(19)
Transaction Costs	29
Foreign Exchange (Gain) Loss, Net	(181)	(404)	854
Re-measurement of Contingent Payment	(80)	164	50
(Gain) Loss on Divestiture of Assets	(81)	(2)	795
Other (Income) Loss, Net	40	9	13
Total Non-operating (Income) Expense	546	597	3,340
Earnings (Loss) From Continuing Operations Before Income Tax	(3,230)	1,397	(3,926)
Income Tax Expense (Recovery)	(851)	(797)	(1,010)
Net Earnings (Loss) From Continuing Operations	(2,379)	2,194	(2,916)
Oil Sands [Member]
Revenues
Gross Sales	7,514	10,838	10,026
Less: Royalties	324	1,143	473
Revenue	7,190	9,695	9,553
Expenses
Transportation and Blending	4,399	5,152	5,879
Operating	1,094	1,039	1,037
Inventory Write-Down (Reversal)	316
(Gain) Loss on Risk Management	268	23	1,551
Operating Margin	1,113	3,481	1,086
Depreciation, Depletion and Amortization	1,684	1,543	1,439
Exploration Expense	9	18	6
Segment Income (Loss)	(580)	1,920	(359)
Conventional [Member]
Revenues
Gross Sales	635	691	904
Less: Royalties	40	30	73
Revenue	595	661	831
Expenses
Transportation and Blending	81	82	90
Operating	318	337	403
(Gain) Loss on Risk Management			26
Operating Margin	196	242	312
Depreciation, Depletion and Amortization	880	319	412
Exploration Expense	82	64	2,117
Segment Income (Loss)	(766)	(141)	(2,217)
Refining and Marketing [Member]
Revenues
Gross Sales	6,051	10,513	11,183
Revenue	6,051	10,513	11,183
Expenses
Purchased Product	5,397	8,795	9,201
Operating	824	948	927
Inventory Write-Down (Reversal)	239	49	60
(Gain) Loss on Risk Management	(21)	(16)	(1)
Operating Margin	(388)	737	996
Depreciation, Depletion and Amortization	739	280	222
Segment Income (Loss)	(1,127)	457	774
Corporate and Eliminations [Member]
Revenues
Gross Sales	(609)	(689)	(724)
Revenue	(609)	(689)	(724)
Expenses
Purchased Product	(278)	(417)	(517)
Transportation and Blending	(36)	(50)	(27)
Operating	(306)	(236)	(183)
(Gain) Loss on Risk Management	61	149	(1,271)
Depreciation, Depletion and Amortization	161	107	58
Segment Income (Loss)	(211)	(242)	1,216
General and Administrative	292	331	1,020
Finance Costs	536	511	627
Interest Income	(9)	(12)	(19)
Transaction Costs	29
Foreign Exchange (Gain) Loss, Net	(181)	(404)	854
Re-measurement of Contingent Payment	(80)	164	50
(Gain) Loss on Divestiture of Assets	(81)	(2)	795
Other (Income) Loss, Net	40	9	13
Total Non-operating (Income) Expense	$ 546	$ 597	$ 3,340

Description of Business and S_5

Description of Business and Segmented Disclosures - Schedule of Revenues by Product (Detail) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure Of Reportable Segments [Line Items]
Refined Products	$ 4,734	$ 8,291	$ 9,032
Market Optimization	1,317	2,222	2,151
Corporate and Eliminations	(609)	(689)	(724)
Revenue	13,227	20,180	20,843
Upstream [Member]
Disclosure Of Reportable Segments [Line Items]
Crude Oil	7,270	9,790	9,662
NGLs	142	202	333
Natural Gas	315	299	320
Other	$ 58	$ 65	$ 69

Description of Business and S_6

Description of Business and Segmented Disclosures - Schedule of Geographical Information (Detail) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure Of Geographical Areas [Line Items]
Revenue	$ 13,227	$ 20,180	$ 20,843
Non-Current Assets	29,758	32,429
Canada [Member]
Disclosure Of Geographical Areas [Line Items]
Revenue	8,399	11,798	11,694
Non-Current Assets	26,168	28,336
United States [Member]
Disclosure Of Geographical Areas [Line Items]
Revenue	4,828	8,382	$ 9,149
Non-Current Assets	$ 3,590	$ 4,093

Description of Business and S_7

Description of Business and Segmented Disclosures - Schedule of Assets by Segment (Detail) - CAD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure Of Reportable Segments [Line Items]
E&E Assets	$ 623	$ 787
PP&E	25,411	27,834	$ 28,698
ROU Assets	1,139	1,325	$ 893
Goodwill	2,272	2,272
Total Assets	32,770	35,713
Oil Sands [Member]
Disclosure Of Reportable Segments [Line Items]
E&E Assets	617	594
PP&E	19,748	20,924
ROU Assets	623	768
Goodwill	2,272	2,272
Total Assets	24,656	26,203
Conventional [Member]
Disclosure Of Reportable Segments [Line Items]
E&E Assets	6	193
PP&E	1,758	2,433
ROU Assets	3	3
Total Assets	1,953	2,754
Refining and Marketing [Member]
Disclosure Of Reportable Segments [Line Items]
PP&E	3,652	4,131
ROU Assets	79	77
Total Assets	4,951	5,688
Corporate and Eliminations [Member]
Disclosure Of Reportable Segments [Line Items]
PP&E	253	346
ROU Assets	434	477
Total Assets	$ 1,210	$ 1,068

Description of Business and S_8

Description of Business and Segmented Disclosures - Schedule of Capital Expenditures (Detail) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure Of Reportable Segments [Line Items]
Capital Investment	$ 841	$ 1,176	$ 1,363
Total Capital Expenditures	859	1,189	1,704
Oil Sands [Member]
Disclosure Of Reportable Segments [Line Items]
Capital Investment	427	656	870
Acquisition Capital	6	2	319
Conventional [Member]
Disclosure Of Reportable Segments [Line Items]
Capital Investment	78	103	228
Acquisition Capital	12	7	22
Refining and Marketing [Member]
Disclosure Of Reportable Segments [Line Items]
Capital Investment	276	280	208
Acquisition Capital		4
Corporate and Eliminations [Member]
Disclosure Of Reportable Segments [Line Items]
Capital Investment	$ 60	$ 137	$ 57

Summary of Significant Accoun_3

Summary of Significant Accounting Policies - Additional information (Detail)	12 Months Ended
	Dec. 31, 2020$ / shares
Disclosure Of Summary Of Significant Accounting Policies [Line Items]
Term of payments due date upon revenue recognition	30 days
Description of payment terms	Cenovus’s revenue transactions do not contain significant financing components and payments are typically due within 30 days of revenue recognition. The Company does not adjust transaction prices for the effects of a significant financing component when the period between the transfer of the promised goods or services to the customer and payment by the customer is less than one year. The Company does not disclose or quantify information about remaining performance obligations that have an original expected duration of one year or less and it does not have any long-term contracts with unfulfilled performance obligations.
Other Upstream Assets [Member]
Disclosure Of Summary Of Significant Accounting Policies [Line Items]
Useful lives of assets	3 years
Land Improvements and Buildings [Member] | Bottom of Range [Member] | Refining Assets [Member]
Disclosure Of Summary Of Significant Accounting Policies [Line Items]
Useful lives of assets	25 years
Land Improvements and Buildings [Member] | Top of Range [Member] | Refining Assets [Member]
Disclosure Of Summary Of Significant Accounting Policies [Line Items]
Useful lives of assets	40 years
Office Equipment and Vehicles [Member] | Bottom of Range [Member] | Refining Assets [Member]
Disclosure Of Summary Of Significant Accounting Policies [Line Items]
Useful lives of assets	3 years
Office Equipment and Vehicles [Member] | Top of Range [Member] | Refining Assets [Member]
Disclosure Of Summary Of Significant Accounting Policies [Line Items]
Useful lives of assets	15 years
Refining Equipment [Member] | Bottom of Range [Member] | Refining Assets [Member]
Disclosure Of Summary Of Significant Accounting Policies [Line Items]
Useful lives of assets	10 years
Refining Equipment [Member] | Top of Range [Member] | Refining Assets [Member]
Disclosure Of Summary Of Significant Accounting Policies [Line Items]
Useful lives of assets	60 years
Other [Member] | Bottom of Range [Member]
Disclosure Of Summary Of Significant Accounting Policies [Line Items]
Useful lives of assets	3 years
Other [Member] | Top of Range [Member]
Disclosure Of Summary Of Significant Accounting Policies [Line Items]
Useful lives of assets	60 years
Employee Incentive Benefit Plan [Member]
Disclosure Of Summary Of Significant Accounting Policies [Line Items]
Target share price	$ 20

Critical Accounting Judgments_2

Critical Accounting Judgments, Key Sources of Estimation Uncertainty and Recent Development - Additional Information (Detail) - JointOperation	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disclosure Of Joint Operations [Line Items]
Number of joint operations	2
WRB [Member]
Disclosure Of Joint Operations [Line Items]
Percent of ownership in joint operations	50.00%	50.00%

General and Administrative - Su

General and Administrative - Summary of General and Administrative Expenses (Detail) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
General And Administrative Expenses [Abstract]
Salaries and Benefits	$ 145	$ 143	$ 205
Administrative and Other	84	95	177
Onerous Contract Provisions (Recovery)	18	(5)	629
Stock-Based Compensation Expense (Note 32)	49	67	9
Other Long-Term Incentive Expense (Recovery)	(4)	31
General and Administrative Expense	$ 292	$ 331	$ 1,020

Finance Costs - Schedule of Fin

Finance Costs - Schedule of Finance Costs (Detail) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Finance Costs [Abstract]
Interest Expense – Short-Term Borrowings and Long-Term Debt	$ 392	$ 407	$ 516
Net (Discount) Premium on Redemption of Long-Term Debt (Note 24)	(25)	(63)	17
Interest Expense – Lease Liabilities (Note 25)	87	82
Unwinding of Discount on Decommissioning Liabilities (Note 27)	57	58	62
Other	25	27	32
Total	$ 536	$ 511	$ 627

Foreign Exchange (Gain) Loss,_3

Foreign Exchange (Gain) Loss, Net - Schedule of Foreign Exchange Gain Loss Net (Detail) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Foreign Exchange Gains Losses:
Unrealized Foreign Exchange (Gain) Loss	$ (131)	$ (827)	$ 649
Realized Foreign Exchange (Gain) Loss	(50)	423	205
Total	(181)	(404)	854
Long-term Borrowings [Member]
Foreign Exchange Gains Losses:
Unrealized Foreign Exchange (Gain) Loss	(194)	(800)	602
Other [Member]
Foreign Exchange Gains Losses:
Unrealized Foreign Exchange (Gain) Loss	$ 63	$ (27)	$ 47

Divestitures - Additional Infor

Divestitures - Additional Information (Detail) - CAD ($) $ / shares in Units, shares in Millions, $ in Millions	Dec. 02, 2020	Dec. 31, 2018
Disclosure Of Disposals [Line Items]
Gain (Loss) before tax on sale of assets		$ 797
Gain (Loss) after tax on sale of assets		557
Marten Hills Oil Assets [Member]
Disclosure Of Disposals [Line Items]
Proceeds from sale of assets	$ 138
Gain (Loss) before tax on sale of assets	79
Gain (Loss) after tax on sale of assets	65
Consideration received as cash	33
Consideration received as common shares	$ 97
Number of shares received as consideration	50
Consideration received as warrants	15
Term of warrants	3 years
Exercise price of warrants	$ 2
Warrants value	$ 8
Gross overriding royalty	$ 41
Cenovus Pipestone Partnership [Member]
Disclosure Of Disposals [Line Items]
Proceeds from sale of assets		$ 625
Wembley Gas Plant [Member]
Disclosure Of Disposals [Line Items]
Percentage of operating working capital interest		39.00%

Other (Income) Loss, Net - Addi

Other (Income) Loss, Net - Additional Information (Detail) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure Other Income And Expense [Line Items]
Other (Income) Loss, Net	$ 40	$ 9	$ 13
Lease income	24	$ 17
Keystone XL Pipeline Project [Member]
Disclosure Other Income And Expense [Line Items]
Other (Income) Loss, Net	100
CEWS Program [Member]
Disclosure Other Income And Expense [Line Items]
Other income	$ 40

Impairment Charges and Revers_3

Impairment Charges and Reversals - Additional Information (Detail)	Dec. 31, 2020CAD ($)	Sep. 30, 2020CAD ($)$ / bbl	Mar. 31, 2020CAD ($)	Dec. 31, 2020CAD ($)	Mar. 31, 2020CAD ($)	Dec. 31, 2018CAD ($)	Dec. 31, 2020CAD ($)	Dec. 31, 2019CAD ($)	Dec. 31, 2018CAD ($)	Dec. 31, 2017CAD ($)
Disclosure Of Information For Each Material Impairment Loss Recognised Or Reversed For Individual Asset Or Cashgenerating Unit [Line Items]
Goodwill impairments					$ 0		$ 0	$ 0
Exploration Expense							91,000,000	82,000,000	$ 2,123,000,000
E&E Asset [Member]
Disclosure Of Information For Each Material Impairment Loss Recognised Or Reversed For Individual Asset Or Cashgenerating Unit [Line Items]
Exploration Expense							$ 91,000,000	82,000,000
PP&E [Member]
Disclosure Of Information For Each Material Impairment Loss Recognised Or Reversed For Individual Asset Or Cashgenerating Unit [Line Items]
CGU Impairments								52,000,000
Discounted Cash Flow [Member]
Disclosure Of Information For Each Material Impairment Loss Recognised Or Reversed For Individual Asset Or Cashgenerating Unit [Line Items]
Discounted future cash flows, discount rate	10.00%			10.00%			10.00%
Discounted future cash flows, inflation rate	2.00%			2.00%			2.00%
Refining Commodity Price Assumptions [Member] | 2035 [Member]
Disclosure Of Information For Each Material Impairment Loss Recognised Or Reversed For Individual Asset Or Cashgenerating Unit [Line Items]
Average Annual Increase Thereafter		2.00%
Bottom of Range [Member] | Discounted Cash Flow [Member]
Disclosure Of Information For Each Material Impairment Loss Recognised Or Reversed For Individual Asset Or Cashgenerating Unit [Line Items]
Discounted future cash flows, discount rate	10.00%			10.00%			10.00%
Top of Range [Member] | Discounted Cash Flow [Member]
Disclosure Of Information For Each Material Impairment Loss Recognised Or Reversed For Individual Asset Or Cashgenerating Unit [Line Items]
Discounted future cash flows, discount rate	15.00%			15.00%			15.00%
CGUs [Member]
Disclosure Of Information For Each Material Impairment Loss Recognised Or Reversed For Individual Asset Or Cashgenerating Unit [Line Items]
CGU Impairments								0	0
Borger Cash Generating Unit [Member]
Disclosure Of Information For Each Material Impairment Loss Recognised Or Reversed For Individual Asset Or Cashgenerating Unit [Line Items]
Recoverable amount		$ 692,000,000
Wood River Cash Generating Units
Disclosure Of Information For Each Material Impairment Loss Recognised Or Reversed For Individual Asset Or Cashgenerating Unit [Line Items]
CGU Impairments	$ 0	$ 0
WTI to West Texas Sour [Member] | Bottom of Range [Member] | Refining Commodity Price Assumptions [Member] | 2021 to 2022 [Member]
Disclosure Of Information For Each Material Impairment Loss Recognised Or Reversed For Individual Asset Or Cashgenerating Unit [Line Items]
Average Price | $ / bbl		36.36
WTI to West Texas Sour [Member] | Bottom of Range [Member] | Refining Commodity Price Assumptions [Member] | 2023 to 2025 [Member]
Disclosure Of Information For Each Material Impairment Loss Recognised Or Reversed For Individual Asset Or Cashgenerating Unit [Line Items]
Average Price | $ / bbl		49.66
WTI to West Texas Sour [Member] | Top of Range [Member] | Refining Commodity Price Assumptions [Member] | 2021 to 2022 [Member]
Disclosure Of Information For Each Material Impairment Loss Recognised Or Reversed For Individual Asset Or Cashgenerating Unit [Line Items]
Average Price | $ / bbl		50.84
WTI to West Texas Sour [Member] | Top of Range [Member] | Refining Commodity Price Assumptions [Member] | 2023 to 2025 [Member]
Disclosure Of Information For Each Material Impairment Loss Recognised Or Reversed For Individual Asset Or Cashgenerating Unit [Line Items]
Average Price | $ / bbl		58.74
WTI to West Texas Sour DIFFERENTIAL [Member] | Bottom of Range [Member] | Refining Commodity Price Assumptions [Member] | 2021 to 2022 [Member]
Disclosure Of Information For Each Material Impairment Loss Recognised Or Reversed For Individual Asset Or Cashgenerating Unit [Line Items]
Average Price | $ / bbl		0.37
WTI to West Texas Sour DIFFERENTIAL [Member] | Bottom of Range [Member] | Refining Commodity Price Assumptions [Member] | 2023 to 2025 [Member]
Disclosure Of Information For Each Material Impairment Loss Recognised Or Reversed For Individual Asset Or Cashgenerating Unit [Line Items]
Average Price | $ / bbl		1.21
WTI to West Texas Sour DIFFERENTIAL [Member] | Top of Range [Member] | Refining Commodity Price Assumptions [Member] | 2021 to 2022 [Member]
Disclosure Of Information For Each Material Impairment Loss Recognised Or Reversed For Individual Asset Or Cashgenerating Unit [Line Items]
Average Price | $ / bbl		1.73
WTI to West Texas Sour DIFFERENTIAL [Member] | Top of Range [Member] | Refining Commodity Price Assumptions [Member] | 2023 to 2025 [Member]
Disclosure Of Information For Each Material Impairment Loss Recognised Or Reversed For Individual Asset Or Cashgenerating Unit [Line Items]
Average Price | $ / bbl		1.81
Group 3 Forward Market Crack Spread [Member] | Bottom of Range [Member] | Refining Commodity Price Assumptions [Member] | 2021 to 2022 [Member]
Disclosure Of Information For Each Material Impairment Loss Recognised Or Reversed For Individual Asset Or Cashgenerating Unit [Line Items]
Average Price | $ / bbl		11.56
Group 3 Forward Market Crack Spread [Member] | Bottom of Range [Member] | Refining Commodity Price Assumptions [Member] | 2023 to 2025 [Member]
Disclosure Of Information For Each Material Impairment Loss Recognised Or Reversed For Individual Asset Or Cashgenerating Unit [Line Items]
Average Price | $ / bbl		11.79
Group 3 Forward Market Crack Spread [Member] | Top of Range [Member] | Refining Commodity Price Assumptions [Member] | 2021 to 2022 [Member]
Disclosure Of Information For Each Material Impairment Loss Recognised Or Reversed For Individual Asset Or Cashgenerating Unit [Line Items]
Average Price | $ / bbl		13.23
Group 3 Forward Market Crack Spread [Member] | Top of Range [Member] | Refining Commodity Price Assumptions [Member] | 2023 to 2025 [Member]
Disclosure Of Information For Each Material Impairment Loss Recognised Or Reversed For Individual Asset Or Cashgenerating Unit [Line Items]
Average Price | $ / bbl		16.58
Railcar CGUs [Member]
Disclosure Of Information For Each Material Impairment Loss Recognised Or Reversed For Individual Asset Or Cashgenerating Unit [Line Items]
CGU Impairments			$ 3,000,000
Conventional [Member]
Disclosure Of Information For Each Material Impairment Loss Recognised Or Reversed For Individual Asset Or Cashgenerating Unit [Line Items]
Exploration Expense							$ 82,000,000	64,000,000	2,117,000,000
Conventional [Member] | E&E Asset [Member]
Disclosure Of Information For Each Material Impairment Loss Recognised Or Reversed For Individual Asset Or Cashgenerating Unit [Line Items]
Exploration Expense							82,000,000	64,000,000	2,100,000,000
Conventional [Member] | PP&E [Member]
Disclosure Of Information For Each Material Impairment Loss Recognised Or Reversed For Individual Asset Or Cashgenerating Unit [Line Items]
CGU Impairments							4,000,000
Conventional [Member] | Clearwater CGU [Member]
Disclosure Of Information For Each Material Impairment Loss Recognised Or Reversed For Individual Asset Or Cashgenerating Unit [Line Items]
CGU Impairments									100,000,000	$ 56,000,000
Recoverable amount						$ 761,000,000			761,000,000
Reversed of impairment loss						$ 132,000,000
Conventional [Member] | CGUs [Member]
Disclosure Of Information For Each Material Impairment Loss Recognised Or Reversed For Individual Asset Or Cashgenerating Unit [Line Items]
CGU Impairments				$ 240,000,000	$ 315,000,000
Refining and Marketing [Member] | Borger Cash Generating Unit [Member]
Disclosure Of Information For Each Material Impairment Loss Recognised Or Reversed For Individual Asset Or Cashgenerating Unit [Line Items]
CGU Impairments		$ 450,000,000
Oil Sands [Member]
Disclosure Of Information For Each Material Impairment Loss Recognised Or Reversed For Individual Asset Or Cashgenerating Unit [Line Items]
Exploration Expense							9,000,000	18,000,000	$ 6,000,000
Oil Sands [Member] | E&E Asset [Member]
Disclosure Of Information For Each Material Impairment Loss Recognised Or Reversed For Individual Asset Or Cashgenerating Unit [Line Items]
Exploration Expense							9,000,000	$ 18,000,000
Oil Sands [Member] | PP&E [Member]
Disclosure Of Information For Each Material Impairment Loss Recognised Or Reversed For Individual Asset Or Cashgenerating Unit [Line Items]
CGU Impairments							$ 48,000,000

Impairment Charges and Revers_4

Impairment Charges and Reversals - Summary of Impairment Losses and Estimated Recoverable Amounts (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2020CAD ($)
Clearwater [Member]
Disclosure Of Information For Each Material Impairment Loss Recognised Or Reversed For Individual Asset Or Cashgenerating Unit [Line Items]
Impairment amount	$ 260
Recoverable amount	160
Elmworth-Wapiti [Member]
Disclosure Of Information For Each Material Impairment Loss Recognised Or Reversed For Individual Asset Or Cashgenerating Unit [Line Items]
Impairment amount	120
Recoverable amount	259
Kaybob-Edson [Member]
Disclosure Of Information For Each Material Impairment Loss Recognised Or Reversed For Individual Asset Or Cashgenerating Unit [Line Items]
Impairment amount	175
Recoverable amount	$ 384

Impairment Charges and Revers_5

Impairment Charges and Reversals - Summary of Forward Prices Used to Determine Future Cash Flows (Detail) - Upstream Commodity Price Assumptions [Member]	Dec. 31, 2020$ / bbl$ / bbl$ / Mcf
WTI [Member]
Disclosure Of Information For Each Material Impairment Loss Recognised Or Reversed For Individual Asset Or Cashgenerating Unit [Line Items]
Average Annual Increase Thereafter	2.00%
WTI [Member] | 2021 [Member]
Disclosure Of Information For Each Material Impairment Loss Recognised Or Reversed For Individual Asset Or Cashgenerating Unit [Line Items]
Average Price	47.17
WTI [Member] | 2022 [Member]
Disclosure Of Information For Each Material Impairment Loss Recognised Or Reversed For Individual Asset Or Cashgenerating Unit [Line Items]
Average Price	50.17
WTI [Member] | 2023 [Member]
Disclosure Of Information For Each Material Impairment Loss Recognised Or Reversed For Individual Asset Or Cashgenerating Unit [Line Items]
Average Price	53.17
WTI [Member] | 2024 [Member]
Disclosure Of Information For Each Material Impairment Loss Recognised Or Reversed For Individual Asset Or Cashgenerating Unit [Line Items]
Average Price	54.97
WTI [Member] | 2025 [Member]
Disclosure Of Information For Each Material Impairment Loss Recognised Or Reversed For Individual Asset Or Cashgenerating Unit [Line Items]
Average Price	56.07
WCS [Member]
Disclosure Of Information For Each Material Impairment Loss Recognised Or Reversed For Individual Asset Or Cashgenerating Unit [Line Items]
Average Annual Increase Thereafter	2.00%
WCS [Member] | 2021 [Member]
Disclosure Of Information For Each Material Impairment Loss Recognised Or Reversed For Individual Asset Or Cashgenerating Unit [Line Items]
Average Price	44.63
WCS [Member] | 2022 [Member]
Disclosure Of Information For Each Material Impairment Loss Recognised Or Reversed For Individual Asset Or Cashgenerating Unit [Line Items]
Average Price	48.18
WCS [Member] | 2023 [Member]
Disclosure Of Information For Each Material Impairment Loss Recognised Or Reversed For Individual Asset Or Cashgenerating Unit [Line Items]
Average Price	52.10
WCS [Member] | 2024 [Member]
Disclosure Of Information For Each Material Impairment Loss Recognised Or Reversed For Individual Asset Or Cashgenerating Unit [Line Items]
Average Price	54.10
WCS [Member] | 2025 [Member]
Disclosure Of Information For Each Material Impairment Loss Recognised Or Reversed For Individual Asset Or Cashgenerating Unit [Line Items]
Average Price	55.19
Edmonton C5+ [Member]
Disclosure Of Information For Each Material Impairment Loss Recognised Or Reversed For Individual Asset Or Cashgenerating Unit [Line Items]
Average Annual Increase Thereafter	2.00%
Edmonton C5+ [Member] | 2021 [Member]
Disclosure Of Information For Each Material Impairment Loss Recognised Or Reversed For Individual Asset Or Cashgenerating Unit [Line Items]
Average Price	59.24
Edmonton C5+ [Member] | 2022 [Member]
Disclosure Of Information For Each Material Impairment Loss Recognised Or Reversed For Individual Asset Or Cashgenerating Unit [Line Items]
Average Price	63.19
Edmonton C5+ [Member] | 2023 [Member]
Disclosure Of Information For Each Material Impairment Loss Recognised Or Reversed For Individual Asset Or Cashgenerating Unit [Line Items]
Average Price	67.34
Edmonton C5+ [Member] | 2024 [Member]
Disclosure Of Information For Each Material Impairment Loss Recognised Or Reversed For Individual Asset Or Cashgenerating Unit [Line Items]
Average Price	69.77
Edmonton C5+ [Member] | 2025 [Member]
Disclosure Of Information For Each Material Impairment Loss Recognised Or Reversed For Individual Asset Or Cashgenerating Unit [Line Items]
Average Price	71.18
AECO [Member]
Disclosure Of Information For Each Material Impairment Loss Recognised Or Reversed For Individual Asset Or Cashgenerating Unit [Line Items]
Average Annual Increase Thereafter	2.00%
AECO [Member] | 2021 [Member]
Disclosure Of Information For Each Material Impairment Loss Recognised Or Reversed For Individual Asset Or Cashgenerating Unit [Line Items]
Average Price | $ / Mcf	2.88
AECO [Member] | 2022 [Member]
Disclosure Of Information For Each Material Impairment Loss Recognised Or Reversed For Individual Asset Or Cashgenerating Unit [Line Items]
Average Price | $ / Mcf	2.80
AECO [Member] | 2023 [Member]
Disclosure Of Information For Each Material Impairment Loss Recognised Or Reversed For Individual Asset Or Cashgenerating Unit [Line Items]
Average Price | $ / Mcf	2.71
AECO [Member] | 2024 [Member]
Disclosure Of Information For Each Material Impairment Loss Recognised Or Reversed For Individual Asset Or Cashgenerating Unit [Line Items]
Average Price | $ / Mcf	2.75
AECO [Member] | 2025 [Member]
Disclosure Of Information For Each Material Impairment Loss Recognised Or Reversed For Individual Asset Or Cashgenerating Unit [Line Items]
Average Price | $ / Mcf	2.80

Impairment Charges and Revers_6

Impairment Charges and Reversals - Summary of Increase (Decrease) to Recoverable Amount (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2020CAD ($)
Clearwater [Member] | One Percent Increase in the Discount Rate [Member]
Disclosure of estimation uncertainty with significant risk of causing material adjustment [line items]
Increase (decrease) to recoverable amount	$ (5)
Clearwater [Member] | One Percent Decrease in the Discount Rate [Member]
Disclosure of estimation uncertainty with significant risk of causing material adjustment [line items]
Increase (decrease) to recoverable amount	6
Clearwater [Member] | Five Percent Increase in the Forward Price Estimates [Member]
Disclosure of estimation uncertainty with significant risk of causing material adjustment [line items]
Increase (decrease) to recoverable amount	52
Clearwater [Member] | Five Percent Decrease in the Forward Price Estimates [Member]
Disclosure of estimation uncertainty with significant risk of causing material adjustment [line items]
Increase (decrease) to recoverable amount	(97)
Elmworth-Wapiti [Member] | One Percent Increase in the Discount Rate [Member]
Disclosure of estimation uncertainty with significant risk of causing material adjustment [line items]
Increase (decrease) to recoverable amount	(7)
Elmworth-Wapiti [Member] | One Percent Decrease in the Discount Rate [Member]
Disclosure of estimation uncertainty with significant risk of causing material adjustment [line items]
Increase (decrease) to recoverable amount	8
Elmworth-Wapiti [Member] | Five Percent Increase in the Forward Price Estimates [Member]
Disclosure of estimation uncertainty with significant risk of causing material adjustment [line items]
Increase (decrease) to recoverable amount	54
Elmworth-Wapiti [Member] | Five Percent Decrease in the Forward Price Estimates [Member]
Disclosure of estimation uncertainty with significant risk of causing material adjustment [line items]
Increase (decrease) to recoverable amount	(96)
Kaybob-Edson [Member] | One Percent Increase in the Discount Rate [Member]
Disclosure of estimation uncertainty with significant risk of causing material adjustment [line items]
Increase (decrease) to recoverable amount	(13)
Kaybob-Edson [Member] | One Percent Decrease in the Discount Rate [Member]
Disclosure of estimation uncertainty with significant risk of causing material adjustment [line items]
Increase (decrease) to recoverable amount	14
Kaybob-Edson [Member] | Five Percent Increase in the Forward Price Estimates [Member]
Disclosure of estimation uncertainty with significant risk of causing material adjustment [line items]
Increase (decrease) to recoverable amount	54
Kaybob-Edson [Member] | Five Percent Decrease in the Forward Price Estimates [Member]
Disclosure of estimation uncertainty with significant risk of causing material adjustment [line items]
Increase (decrease) to recoverable amount	(106)
Borger [Member] | One Percent Increase in the Discount Rate [Member]
Disclosure of estimation uncertainty with significant risk of causing material adjustment [line items]
Increase (decrease) to recoverable amount	(71)
Borger [Member] | One Percent Decrease in the Discount Rate [Member]
Disclosure of estimation uncertainty with significant risk of causing material adjustment [line items]
Increase (decrease) to recoverable amount	81
Borger [Member] | Five Percent Increase in the Forward Price Estimates [Member]
Disclosure of estimation uncertainty with significant risk of causing material adjustment [line items]
Increase (decrease) to recoverable amount	263
Borger [Member] | Five Percent Decrease in the Forward Price Estimates [Member]
Disclosure of estimation uncertainty with significant risk of causing material adjustment [line items]
Increase (decrease) to recoverable amount	$ (264)

Discontinued Operations - Addit

Discontinued Operations - Additional Information (Detail) - CAD ($) $ in Millions	Jan. 05, 2018	Dec. 31, 2018
Disclosure Of Discontinued Operations [Line Items]
Net Earnings (Loss) From Discontinued Operations		$ 247
Suffield Divestiture [Member]
Disclosure Of Discontinued Operations [Line Items]
Cash proceeds from sale of assets	$ 512
Gain (Loss) before tax on sale of assets	$ 343
Conventional [Member]
Disclosure Of Discontinued Operations [Line Items]
Net Earnings (Loss) From Discontinued Operations		247
Cash flows from (used in) operating activities, discontinued operations		36
Cash flows from (used in) investing activities, discontinued operations		$ 404

Income Taxes - Provision for In

Income Taxes - Provision for Income Taxes (Detail) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Major Components Of Tax Expense Income [Line Items]
Current Tax Expense (Recovery)	$ (13)	$ 17	$ (126)
Deferred Tax Expense (Recovery)	(838)	(814)	(884)
Tax Expense (Recovery) From Continuing Operations	(851)	(797)	(1,010)
Canada [Member]
Major Components Of Tax Expense Income [Line Items]
Current Tax Expense (Recovery)	(14)	14	(128)
United States [Member]
Major Components Of Tax Expense Income [Line Items]
Current Tax Expense (Recovery)	$ 1	$ 3	$ 2

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - CAD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure of income taxes [line items]
Canadian Statutory Tax Rate	24.00%	26.50%	27.00%
Deferred tax (expense) recovery		$ 387,000,000	$ 78,000,000
Deferred income tax assets has been recognized	$ 36,000,000
Deferred tax liability has been recognized	0	0
Amounts of tax pools available, including tax losses	9,657,000,000	8,761,000,000
Net capital losses recognized as a deferred income tax asset	22,000,000	100,000,000
Canadian Federal Non Capital Losses [Member]
Disclosure of income taxes [line items]
Amounts of tax pools available, including tax losses	1,682,000,000	696,000,000
US Federal Net Operating Losses [Member]
Disclosure of income taxes [line items]
Amounts of tax pools available, including tax losses	1,084,000,000	188,000,000
Canadian Net Capital Losses [Member]
Disclosure of income taxes [line items]
Amounts of tax pools available, including tax losses	85,000,000	188,000,000
Net capital losses associated with unrealized foreign exchange losses	$ 254,000,000	262,000,000
Internal Restructuring [Member]
Disclosure of income taxes [line items]
Deferred tax (expense) recovery		$ 387,000,000
Alberta [Member]
Disclosure of income taxes [line items]
Canadian Statutory Tax Rate	8.00%	8.00%	12.00%
Reduction in provincial corporate tax rate enacted period		4 years
Deferred tax (expense) recovery		$ 671,000,000

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of Income Taxes Calculated at Statutory Rate (Detail) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Reconciliation Of Average Effective Tax Rate And Applicable Tax Rate [Abstract]
Earnings (Loss) From Continuing Operations Before Income Tax	$ (3,230)	$ 1,397	$ (3,926)
Canadian Statutory Rate	24.00%	26.50%	27.00%
Expected Income Tax Expense (Recovery) From Continuing Operations	$ (775)	$ 370	$ (1,060)
Effect on Taxes Resulting From:
Statutory and Other Rate Differences	19	(52)	(57)
Non-Taxable Capital (Gains) Losses	(42)	(38)	89
Non-Recognition of Capital (Gains) Losses	(42)	(39)	87
Adjustments Arising From Prior Year Tax Filings	(8)	4	3
Recognition of U.S. Tax Basis		(387)	(78)
Alberta Corporate Rate Reduction	(7)	(671)
Other	4	16	6
Tax Expense (Recovery) From Continuing Operations	$ (851)	$ (797)	$ (1,010)
Effective Tax Rate	26.30%	(57.10%)	25.70%

Income Taxes - Deferred Income

Income Taxes - Deferred Income Tax Liabilities and Deferred Income Tax Assets (Detail) - CAD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure of income taxes [line items]
Deferred Income Tax Liabilities	$ 4,146	$ 4,543	$ 5,545
Deferred Income Tax Assets	(948)	(511)	(684)
Net Deferred Income Tax Liability	3,198	4,032	$ 4,861
Less Than 1 Year [Member]
Disclosure of income taxes [line items]
Deferred Income Tax Liabilities		3
Deferred Income Tax Assets	(88)	(113)
1 Year [Member]
Disclosure of income taxes [line items]
Deferred Income Tax Liabilities	4,146	4,540
Deferred Income Tax Assets	$ (860)	$ (398)

Income Taxes - Schedule of Move

Income Taxes - Schedule of Movement in Deferred Income Tax Liabilities and Assets (Detail) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Reconciliation Of Changes In Deferred Tax Liability Asset [Line Items]
Deferred Income Tax Liabilities, Beginning Balance	$ 4,543	$ 5,545
Deferred Income Tax Liabilities, Ending Balance	4,146	4,543
Deferred Income Tax Assets, Beginning Balance	(511)	(684)
Deferred Income Tax Assets, Ending Balance	(948)	(511)
Net Deferred Income Tax Liabilities, Beginning Balance	4,032	4,861
Net Deferred Income Tax Liabilities, Ending Balance	3,198	4,032
Unused Tax Losses [Member]
Reconciliation Of Changes In Deferred Tax Liability Asset [Line Items]
Deferred Income Tax Assets, Beginning Balance	(225)	(357)
Deferred Income Tax Assets, Ending Balance	(659)	(225)
Deferred Income Tax Liabilities [Member]
Reconciliation Of Changes In Deferred Tax Liability Asset [Line Items]
Charged (Credited) to Earnings	(390)	(977)
Charged (Credited) to OCI	(7)	(25)
Deferred Income Tax Assets [Member]
Reconciliation Of Changes In Deferred Tax Liability Asset [Line Items]
Charged (Credited) to Earnings	(448)	163
Charged (Credited) to OCI	11	10
Deferred Income Tax Assets [Member] | Unused Tax Losses [Member]
Reconciliation Of Changes In Deferred Tax Liability Asset [Line Items]
Charged (Credited) to Earnings	(448)	129
Charged (Credited) to OCI	14	3
Net Deferred Income Tax Liabilities [Member]
Reconciliation Of Changes In Deferred Tax Liability Asset [Line Items]
Charged (Credited) to Earnings	(838)	(814)
Charged (Credited) to OCI	4	(15)
PP&E [Member]
Reconciliation Of Changes In Deferred Tax Liability Asset [Line Items]
Deferred Income Tax Liabilities, Beginning Balance	4,498	5,450
Deferred Income Tax Liabilities, Ending Balance	4,124	4,498
PP&E [Member] | Deferred Income Tax Liabilities [Member]
Reconciliation Of Changes In Deferred Tax Liability Asset [Line Items]
Charged (Credited) to Earnings	(367)	(927)
Charged (Credited) to OCI	(7)	(25)
Risk Management [Member]
Reconciliation Of Changes In Deferred Tax Liability Asset [Line Items]
Deferred Income Tax Liabilities, Beginning Balance	1	44
Deferred Income Tax Liabilities, Ending Balance		1
Deferred Income Tax Assets, Beginning Balance	(1)	(1)
Deferred Income Tax Assets, Ending Balance	(13)	(1)
Risk Management [Member] | Deferred Income Tax Liabilities [Member]
Reconciliation Of Changes In Deferred Tax Liability Asset [Line Items]
Charged (Credited) to Earnings	(1)	(43)
Risk Management [Member] | Deferred Income Tax Assets [Member]
Reconciliation Of Changes In Deferred Tax Liability Asset [Line Items]
Charged (Credited) to Earnings	(12)
Other [Member]
Reconciliation Of Changes In Deferred Tax Liability Asset [Line Items]
Deferred Income Tax Liabilities, Beginning Balance	44	51
Deferred Income Tax Liabilities, Ending Balance	22	44
Deferred Income Tax Assets, Beginning Balance	(285)	(326)
Deferred Income Tax Assets, Ending Balance	(276)	(285)
Other [Member] | Deferred Income Tax Liabilities [Member]
Reconciliation Of Changes In Deferred Tax Liability Asset [Line Items]
Charged (Credited) to Earnings	(22)	(7)
Other [Member] | Deferred Income Tax Assets [Member]
Reconciliation Of Changes In Deferred Tax Liability Asset [Line Items]
Charged (Credited) to Earnings	12	34
Charged (Credited) to OCI	$ (3)	$ 7

Income Taxes - Schedule of Amou

Income Taxes - Schedule of Amounts of Tax Pools Available, Including Tax Losses (Detail) - CAD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Amounts of tax pools available, including tax losses	$ 9,657	$ 8,761
Canada [Member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Amounts of tax pools available, including tax losses	6,540	6,113
United States [Member]
Disclosure of temporary difference, unused tax losses and unused tax credits [Line Items]
Amounts of tax pools available, including tax losses	$ 3,117	$ 2,648

Per Share Amounts - Schedule Re

Per Share Amounts - Schedule Representing Per Share Amounts (Detail) - CAD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Earnings (Loss) From:
Continuing Operations	$ (2,379)	$ 2,194	$ (2,916)
Discontinued Operations			247
Net Earnings (Loss)	$ (2,379)	$ 2,194	$ (2,669)
Basic – Weighted Average Number of Shares	1,228.9	1,228.8	1,228.8
Dilutive Effect of Cenovus Net Settlement Rights		0.6	0.4
Diluted – Weighted Average Number of Shares	1,228.9	1,229.4	1,229.2
Basic and Diluted Earnings (Loss) Per Share ($)
Continuing Operations	$ (1.94)	$ 1.78	$ (2.37)
Discontinued Operations			0.20
Net Earnings (Loss) Per Share	$ (1.94)	$ 1.78	$ (2.17)

Per Share Amounts - Additional

Per Share Amounts - Additional Information (Detail) - CAD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Earnings Per Share [Line Items]
Dividends paid on common shares		$ 77	$ 260	$ 245
Common Share [Member]
Earnings Per Share [Line Items]
Dividends paid on common shares	$ 77		$ 260	$ 245
Dividend paid per share	$ 0.0625		$ 0.2125	$ 0.20
Dividend declared but not paid		$ 0.0175
Dividends payable date		Mar. 31, 2021
Dividends payables date of record		Mar. 15, 2021
Preferred Share [Member]
Earnings Per Share [Line Items]
Dividends payable date		Mar. 31, 2021
Dividend declared but not paid to preferred shareholders		$ 8
NSRs [Member]
Earnings Per Share [Line Items]
Options excluded from diluted weighted average number of shares		31	32	34

Cash and Cash Equivalents - Sch

Cash and Cash Equivalents - Schedule Representing Cash and Cash Equivalents (Detail) - CAD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash And Cash Equivalents [Abstract]
Cash	$ 368	$ 108
Short-Term Investments	10	78
Total	$ 378	$ 186	$ 781	$ 610

Accounts Receivables and Accrue

Accounts Receivables and Accrued Revenues - Schedule of accounts receivables and accrued revenues (Detail) - CAD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Trade And Other Current Receivables [Abstract]
Accruals	$ 1,053	$ 1,221
Prepaids and Deposits	121	54
Partner Advances	175	16
Trade	96	212
Joint Operations Receivables	35	36
Other	8	17
Accounts Receivable and Accrued Revenues	$ 1,488	$ 1,556

Inventories - Schedule of Inven

Inventories - Schedule of Inventories (Detail) - CAD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Disclosure of inventories [line items]
Parts and Supplies	$ 93	$ 87
Inventories	1,089	1,532
Refining and Marketing [Member]
Disclosure of inventories [line items]
Refining and Marketing	613	874
Oil Sands [Member]
Disclosure of inventories [line items]
Crude Oil	382	570
Conventional [Member]
Disclosure of inventories [line items]
Crude Oil	$ 1	$ 1

Inventories - Additional Inform

Inventories - Additional Information (Detail) - CAD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure of inventories [line items]
Cost of inventories recognized as expense during period		$ 9,996	$ 14,285	$ 15,664
Realized inventory write-down	$ 547
Crude Oil Blend, Condensate and Refined Product Inventory [Member]
Disclosure of inventories [line items]
Inventory write-downs	$ 588
Reversed inventory write downs		39
Refined Product Inventory [Member]
Disclosure of inventories [line items]
Inventory write-downs		$ 6	$ 25

Exploration and Evaluation As_3

Exploration and Evaluation Assets - Summary of Exploration and Valuation Assets (Detail) - CAD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure Of Exploration And Evaluation Assets [Line Items]
Beginning Balance		$ 787
Exploration Expense		(91)	$ (82)	$ (2,123)
Ending Balance		623	787
E&E Assets [Member]
Disclosure Of Exploration And Evaluation Assets [Line Items]
Beginning Balance		787	785
Additions		48	73
Transfers to PP&E (Note 18) (1)	[1]	(47)
Exploration Expense		(91)	(82)
Depletion		(18)
Change in Decommissioning Liabilities		5	9
Exchange Rate Movements and Other			2
Divestitures (Note 8)		(61)
Ending Balance		$ 623	$ 787	$ 785
[1]	(1)Includes the $41 million reclassification of the GORR retained in the sale of the Marten Hills assets (see Note 8).

Exploration and Evaluation As_4

Exploration and Evaluation Assets - Summary of Exploration and Valuation Assets (Parenthetical) (Detail) $ in Millions	Dec. 31, 2020CAD ($)
Marten Hills Asset [Member]
Disclosure Of Exploration And Evaluation Assets [Line Items]
Gross overriding royalty	$ 41

Property, Plant and Equipment_3

Property, Plant and Equipment, Net - Summary of Property, Plant and Equipment (Detail) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disclosure Of Property Plant And Equipment [Line Items]
Beginning Balance	$ 27,834	$ 28,698
Ending Balance	25,411	27,834
Cost [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning Balance	36,356	35,224
Adjustment for Change in Accounting Policy		(4)
Additions	811	1,116
Transfers From E&E Assets (Note 17)	47
Change in Decommissioning Liabilities	(6)	354
Exchange Rate Movements and Other	(159)	(294)
Divestitures	(3)	(40)
Ending Balance	37,046	36,356
Accumulated Depreciation, Depletion and Amortization [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning Balance	8,522	6,526
Adjustment for Change in Accounting Policy		(1)
Depreciation, Depletion and Amortization	2,119	2,051
Impairment Charges	1,109	30
Exchange Rate Movements and Other	(115)	(55)
Divestitures		(29)
Ending Balance	11,635	8,522
Development & Production Upstream Assets [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning Balance	23,357	24,128
Ending Balance	21,465	23,357
Development & Production Upstream Assets [Member] | Cost [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning Balance	29,032	28,046
Additions	475	695
Transfers From E&E Assets (Note 17)	6
Change in Decommissioning Liabilities	(11)	340
Exchange Rate Movements and Other	(6)	(9)
Divestitures	(3)	(40)
Ending Balance	29,493	29,032
Development & Production Upstream Assets [Member] | Accumulated Depreciation, Depletion and Amortization [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning Balance	5,675	3,918
Depreciation, Depletion and Amortization	1,768	1,735
Impairment Charges	607	20
Exchange Rate Movements and Other	(22)	31
Divestitures		(29)
Ending Balance	8,028	5,675
Other Upstream Assets [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Ending Balance	41
Other Upstream Assets [Member] | Cost [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning Balance	333	333
Transfers From E&E Assets (Note 17)	41
Ending Balance	374	333
Other Upstream Assets [Member] | Accumulated Depreciation, Depletion and Amortization [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning Balance	333	333
Ending Balance	333	333
Refining Equipment [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning Balance	3,981	4,190
Ending Balance	3,476	3,981
Refining Equipment [Member] | Cost [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning Balance	5,577	5,632
Adjustment for Change in Accounting Policy		(4)
Additions	243	228
Change in Decommissioning Liabilities	3	9
Exchange Rate Movements and Other	(152)	(288)
Ending Balance	5,671	5,577
Refining Equipment [Member] | Accumulated Depreciation, Depletion and Amortization [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning Balance	1,596	1,442
Adjustment for Change in Accounting Policy		(1)
Depreciation, Depletion and Amortization	242	241
Impairment Charges	450
Exchange Rate Movements and Other	(93)	(86)
Ending Balance	2,195	1,596
Other [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning Balance	496	380
Ending Balance	429	496
Other [Member] | Cost [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning Balance	1,414	1,213
Additions	93	193
Change in Decommissioning Liabilities	2	5
Exchange Rate Movements and Other	(1)	3
Ending Balance	1,508	1,414
Other [Member] | Accumulated Depreciation, Depletion and Amortization [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Beginning Balance	918	833
Depreciation, Depletion and Amortization	109	75
Impairment Charges	52	10
Ending Balance	$ 1,079	$ 918

Property, Plant and Equipment_4

Property, Plant and Equipment, Net - Summary of PP&E Under Construction and Not Subject to DD&A (Detail) - CAD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Disclosure Of Property Plant And Equipment [Line Items]
Property Plant and Equipment Temporarily Idle	$ 2,033	$ 2,008
Development & Production Upstream Assets [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Property Plant and Equipment Temporarily Idle	1,807	1,836
Refining Equipment [Member]
Disclosure Of Property Plant And Equipment [Line Items]
Property Plant and Equipment Temporarily Idle	$ 226	$ 172

Right of Use Assets, Net - Summ

Right of Use Assets, Net - Summary of Right of Use Assets, Net (Detail) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disclosure Of Quantitative Information About Rightofuse Assets [Line Items]
Beginning balance	$ 1,325	$ 893
Depreciation	215
Ending balance	1,139	1,325
Cost [Member]
Disclosure Of Quantitative Information About Rightofuse Assets [Line Items]
Beginning balance	1,492	894
Additions	53	624
Terminations	(1)	(11)
Modifications	(2)
Reclassifications	(14)	(8)
Re-measurement	(2)	14
Exchange Rate Movements and Other	(24)	(21)
Ending balance	1,502	1,492
Accumulated Depreciation [Member]
Disclosure Of Quantitative Information About Rightofuse Assets [Line Items]
Beginning balance	167	1
Depreciation		165
Impairment Losses	3	3
Terminations	(1)	(1)
Exchange Rate Movements and Other	(21)	(1)
Ending balance	363	167
Real estate [Member]
Disclosure Of Quantitative Information About Rightofuse Assets [Line Items]
Beginning balance	477	517
Depreciation	27
Ending balance	437	477
Real estate [Member] | Cost [Member]
Disclosure Of Quantitative Information About Rightofuse Assets [Line Items]
Beginning balance	509	517
Additions	1	10
Reclassifications	(14)	(8)
Exchange Rate Movements and Other	(1)	(10)
Ending balance	495	509
Real estate [Member] | Accumulated Depreciation [Member]
Disclosure Of Quantitative Information About Rightofuse Assets [Line Items]
Beginning balance	32
Depreciation		29
Impairment Losses		3
Exchange Rate Movements and Other	(1)
Ending balance	58	32
Railcars & Barges [Member]
Disclosure Of Quantitative Information About Rightofuse Assets [Line Items]
Beginning balance	440	63
Depreciation	86
Ending balance	349	440
Railcars & Barges [Member] | Cost [Member]
Disclosure Of Quantitative Information About Rightofuse Assets [Line Items]
Beginning balance	495	63
Additions	18	436
Re-measurement	(20)	(2)
Exchange Rate Movements and Other	(13)	(2)
Ending balance	480	495
Railcars & Barges [Member] | Accumulated Depreciation [Member]
Disclosure Of Quantitative Information About Rightofuse Assets [Line Items]
Beginning balance	55
Depreciation		55
Impairment Losses	3
Exchange Rate Movements and Other	(13)
Ending balance	131	55
Storage Assets [Member]
Disclosure Of Quantitative Information About Rightofuse Assets [Line Items]
Beginning balance	391	292
Depreciation	95
Ending balance	335	391
Storage Assets [Member] | Cost [Member]
Disclosure Of Quantitative Information About Rightofuse Assets [Line Items]
Beginning balance	464	292
Additions	22	172
Terminations	(1)	(11)
Modifications	1
Re-measurement	19	18
Exchange Rate Movements and Other	(8)	(7)
Ending balance	497	464
Storage Assets [Member] | Accumulated Depreciation [Member]
Disclosure Of Quantitative Information About Rightofuse Assets [Line Items]
Beginning balance	73
Depreciation		75
Terminations	(1)	(1)
Exchange Rate Movements and Other	(5)	(1)
Ending balance	162	73
Refining Equipment [Member]
Disclosure Of Quantitative Information About Rightofuse Assets [Line Items]
Beginning balance	7	12
Depreciation	2
Ending balance	10	7
Refining Equipment [Member] | Cost [Member]
Disclosure Of Quantitative Information About Rightofuse Assets [Line Items]
Beginning balance	10	13
Additions	5
Re-measurement		(2)
Exchange Rate Movements and Other		(1)
Ending balance	15	10
Refining Equipment [Member] | Accumulated Depreciation [Member]
Disclosure Of Quantitative Information About Rightofuse Assets [Line Items]
Beginning balance	3	1
Depreciation		2
Ending balance	5	3
Other assets [member]
Disclosure Of Quantitative Information About Rightofuse Assets [Line Items]
Beginning balance	10	9
Depreciation	5
Ending balance	8	10
Other assets [member] | Cost [Member]
Disclosure Of Quantitative Information About Rightofuse Assets [Line Items]
Beginning balance	14	9
Additions	7	6
Modifications	(3)
Re-measurement	(1)
Exchange Rate Movements and Other	(2)	(1)
Ending balance	15	14
Other assets [member] | Accumulated Depreciation [Member]
Disclosure Of Quantitative Information About Rightofuse Assets [Line Items]
Beginning balance	4
Depreciation		4
Exchange Rate Movements and Other	(2)
Ending balance	$ 7	$ 4

Other Assets - Schedule of Othe

Other Assets - Schedule of Other Assets (Detail) - CAD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Other Noncurrent Assets [Abstract]
Intangible Assets	$ 89	$ 101
Equity Investments	52	52
Investment in Associate	97
Net Investment in Finance Leases	52	30
Long-Term Receivables and Prepaids	11	28
Other	12
Other assets	$ 313	$ 211

Other Assets - Additional Infor

Other Assets - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2020
Intangible Asset [Member]
Other Assets [Line Items]
Cost amortized over the life of contract	10 years

Goodwill - Additional Informati

Goodwill - Additional Information (Detail) - CAD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2020	Dec. 31, 2019
Disclosure Of Information For Individual Asset Or Cashgenerating Unit With Significant Amount Of Goodwill Or Intangible Assets With Indefinite Useful Lives [Line Items]
Goodwill		$ 2,272,000,000	$ 2,272,000,000
Goodwill impairments	$ 0	0	0
Primrose (Foster Creek) [Member]
Disclosure Of Information For Individual Asset Or Cashgenerating Unit With Significant Amount Of Goodwill Or Intangible Assets With Indefinite Useful Lives [Line Items]
Goodwill		1,171,000,000	1,171,000,000
Christina Lake [Member]
Disclosure Of Information For Individual Asset Or Cashgenerating Unit With Significant Amount Of Goodwill Or Intangible Assets With Indefinite Useful Lives [Line Items]
Goodwill		$ 1,101,000,000	$ 1,101,000,000

Accounts Payable and Accrued _3

Accounts Payable and Accrued Liabilities - Schedule of Accounts Payable and Accrued Liabilities (Detail) - CAD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Trade And Other Current Payables [Abstract]
Accruals	$ 912	$ 1,085
Trade	608	954
Interest	77	49
Partner Advances	175	16
Employee Long-Term Incentives	130	60
Joint Operations Payable	6	2
Risk Management	58	2
Onerous Contract Provisions	26	17
Other	26	44
Accounts payable and accrued liabilities	$ 2,018	$ 2,229

Short-Term Borrowings - Additio

Short-Term Borrowings - Additional Information (Details)	Dec. 31, 2020CAD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019CAD ($)
Disclosure of detailed information about borrowings [line items]
Uncommitted demand facilities	$ 1,100,000,000
Amount of drawn facility	0
Outstanding letters of credit	441,000,000		$ 364,000,000
Cenovus Energy Inc. [Member]
Disclosure of detailed information about borrowings [line items]
Amount of drawn facility	121,000,000	$ 95,000,000
WRB [Member]
Disclosure of detailed information about borrowings [line items]
Uncommitted demand facilities		55,000,000
Amount of drawn facility		190,000,000
Top of Range [Member]
Disclosure of detailed information about borrowings [line items]
Uncommitted demand facilities	1,600,000,000
Amount of undrawn facilities for general purposes	$ 600,000,000
Top of Range [Member] | WRB [Member]
Disclosure of detailed information about borrowings [line items]
Borrowing facilities		300,000,000
Top of Range [Member] | WRB [Member] | Cenovus Energy Inc. [Member]
Disclosure of detailed information about borrowings [line items]
Borrowing facilities		$ 150,000,000

Long-term Debt and Capital St_3

Long-term Debt and Capital Structure - Additional Information (Detail) $ in Millions	1 Months Ended	12 Months Ended
	Dec. 31, 2020CAD ($)	Dec. 31, 2020CAD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2020USD ($)	Jul. 30, 2020USD ($)	Dec. 31, 2019CAD ($)	Dec. 31, 2019USD ($)	Sep. 19, 2019USD ($)
Disclosure of detailed information about borrowings [line items]
Weighted average interest rate	4.90%	4.90%		4.90%		5.10%	5.10%
Total Debt Principal				$ 5,898,000,000			$ 4,998,000,000
Committed Credit Facility [Member]
Disclosure of detailed information about borrowings [line items]
Maturity date		Cenovus has in place a committed revolving credit facility that consists of a $1.2 billion tranche and a $3.3 billion tranche with maturity dates of November 30, 2022 and November 30, 2023, respectively. In April 2020, the Company added a committed credit facility with capacity of $1.1 billion to further support the Company’s financial resilience in the current market environment. On December 31, 2020, the Company cancelled the $1.1 billion credit facility.	Cenovus has in place a committed revolving credit facility that consists of a $1.2 billion tranche and a $3.3 billion tranche with maturity dates of November 30, 2022 and November 30, 2023, respectively. In April 2020, the Company added a committed credit facility with capacity of $1.1 billion to further support the Company’s financial resilience in the current market environment. On December 31, 2020, the Company cancelled the $1.1 billion credit facility.
Credit facility cancellation	$ 1,100
Top of Range [Member]
Disclosure of detailed information about borrowings [line items]
Target Net Debt to Adjusted EBITDA Ratio		2	2
Debt to capitalization ratio	65.00%	65.00%		65.00%
Base Shelf Prospectus [Member] | Top of Range [Member]
Disclosure of detailed information about borrowings [line items]
Authorized capacity under base shelf prospectus								$ 5,000,000,000
Tranche One [Member] | Committed Credit Facility [Member]
Disclosure of detailed information about borrowings [line items]
Maturity date		November 30, 2022	November 30, 2022
Tranche One [Member] | Top of Range [Member] | Committed Credit Facility [Member]
Disclosure of detailed information about borrowings [line items]
Committed credit facility capacity	$ 1,100	$ 1,100				$ 1,200
Tranche Two [Member] | Committed Credit Facility [Member]
Disclosure of detailed information about borrowings [line items]
Maturity date		November 30, 2023	November 30, 2023
Tranche Two [Member] | Top of Range [Member] | Committed Credit Facility [Member]
Disclosure of detailed information about borrowings [line items]
Committed credit facility capacity						$ 3,300
Senior Unsecured Notes
Disclosure of detailed information about borrowings [line items]
Total Debt Principal					$ 1,000,000,000
Long-term Borrowings [Member]
Disclosure of detailed information about borrowings [line items]
Payment to repurchase unsecured notes			$ 81,000,000
Unsecured notes principal repurchase				$ 100,000,000
Gain on debt repurchase recorded in finance cost		$ 25

Long-term Debt and Capital St_4

Long-term Debt and Capital Structure - Schedule of Long Term Debt (Detail) - CAD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Disclosure of detailed information about borrowings [line items]
Debt Discounts and Transaction Costs	$ (69)	$ (58)
Long-Term Debt	7,441	6,699
Long-term Borrowings [Member]
Disclosure of detailed information about borrowings [line items]
Total Debt Principal, (CAD equivalent)	7,510	6,757
Long-term Borrowings [Member] | Revolving Term Debt [Member]
Disclosure of detailed information about borrowings [line items]
Revolving Term Debt		265
Long-term Borrowings [Member] | U.S. Dollar Denominated Unsecured Notes [Member]
Disclosure of detailed information about borrowings [line items]
Total Debt Principal, (CAD equivalent)	$ 7,510	$ 6,492

Long-term Debt and Capital St_5

Long-term Debt and Capital Structure - Schedule Remaining Principal Amounts of U.S. Dollar Denominated Unsecured Notes (Detail) $ in Millions, $ in Millions	Dec. 31, 2020CAD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019CAD ($)	Dec. 31, 2019USD ($)
Disclosure of detailed information about borrowings [line items]
Total Debt Principal		$ 5,898		$ 4,998
Long-term Borrowings [Member]
Disclosure of detailed information about borrowings [line items]
Total Debt Principal, (CAD equivalent)	$ 7,510		$ 6,757
3.00% Due August 15, 2022 [Member] | Long-term Borrowings [Member]
Disclosure of detailed information about borrowings [line items]
Total Debt Principal		500		500
Total Debt Principal, (CAD equivalent)	637		650
3.80% Due September 15, 2023 [Member] | Long-term Borrowings [Member]
Disclosure of detailed information about borrowings [line items]
Total Debt Principal		450		450
Total Debt Principal, (CAD equivalent)	573		585
5.38% due July 15, 2025 [Member] | Long-term Borrowings [Member]
Disclosure of detailed information about borrowings [line items]
Total Debt Principal		1,000
Total Debt Principal, (CAD equivalent)	1,273
4.25% Due April 15, 2027 [Member] | Long-term Borrowings [Member]
Disclosure of detailed information about borrowings [line items]
Total Debt Principal		962		962
Total Debt Principal, (CAD equivalent)	1,225		1,249
5.25% Due June 15, 2037 [Member] | Long-term Borrowings [Member]
Disclosure of detailed information about borrowings [line items]
Total Debt Principal		583		641
Total Debt Principal, (CAD equivalent)	742		833
6.75% due November 15, 2039 [Member] | Long-term Borrowings [Member]
Disclosure of detailed information about borrowings [line items]
Total Debt Principal		1,390		1,400
Total Debt Principal, (CAD equivalent)	1,770		1,818
4.45% Due September 15, 2042 [Member] | Long-term Borrowings [Member]
Disclosure of detailed information about borrowings [line items]
Total Debt Principal		155		155
Total Debt Principal, (CAD equivalent)	198		202
5.20% Due September 15, 2043 [Member] | Long-term Borrowings [Member]
Disclosure of detailed information about borrowings [line items]
Total Debt Principal		58		58
Total Debt Principal, (CAD equivalent)	74		75
5.40% Due June 15, 2047 [Member] | Long-term Borrowings [Member]
Disclosure of detailed information about borrowings [line items]
Total Debt Principal		800		832
Total Debt Principal, (CAD equivalent)	1,018		1,080
U.S. Dollar Denominated Unsecured Notes [Member] | Long-term Borrowings [Member]
Disclosure of detailed information about borrowings [line items]
Total Debt Principal		$ 5,898		$ 4,998
Total Debt Principal, (CAD equivalent)	$ 7,510		$ 6,492

Long-term Debt and Capital St_6

Long-term Debt and Capital Structure - Schedule of Mandatory Debt Payments (Detail) $ in Millions, $ in Millions	Dec. 31, 2020CAD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019CAD ($)	Dec. 31, 2019USD ($)
Disclosure of detailed information about borrowings [line items]
Total Debt Principal		$ 5,898		$ 4,998
Long-term Borrowings [Member]
Disclosure of detailed information about borrowings [line items]
Total Debt Principal, (CAD equivalent)	$ 7,510		$ 6,757
Long-term Borrowings [Member] | Later than one year and not later than two years [Member]
Disclosure of detailed information about borrowings [line items]
Total Debt Principal		500
Total Debt Principal, (CAD equivalent)	637
Long-term Borrowings [Member] | Later than two years and not later than three years [Member]
Disclosure of detailed information about borrowings [line items]
Total Debt Principal		450
Total Debt Principal, (CAD equivalent)	573
Long-term Borrowings [Member] | Later than four years and not later than five years [Member]
Disclosure of detailed information about borrowings [line items]
Total Debt Principal		1,000
Total Debt Principal, (CAD equivalent)	1,273
Long-term Borrowings [Member] | Thereafter [Member]
Disclosure of detailed information about borrowings [line items]
Total Debt Principal		3,948
Total Debt Principal, (CAD equivalent)	5,027
U.S. Dollar Denominated Unsecured Notes [Member] | Long-term Borrowings [Member]
Disclosure of detailed information about borrowings [line items]
Total Debt Principal		$ 5,898		$ 4,998
Total Debt Principal, (CAD equivalent)	$ 7,510		$ 6,492

Long-term Debt and Capital St_7

Long-term Debt and Capital Structure - Summary of Net Debt to Adjusted EBITDA (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2020CAD ($)	Dec. 31, 2019CAD ($)	Dec. 31, 2018CAD ($)	Dec. 31, 2017CAD ($)
Disclosure Of Objectives Policies And Processes For Managing Capital [Line Items]
Short-Term Borrowings	$ 121
Long-Term Debt	7,441	$ 6,699
Less: Cash and Cash Equivalents	(378)	(186)	$ (781)	$ (610)
Net Debt	7,184	6,513	8,383
Net Earnings (Loss)	(2,379)	2,194	(2,669)
Add (Deduct):
Interest Income	(9)	(12)	(19)
Foreign Exchange (Gain) Loss, Net	(181)	(404)	854
Re-measurement of Contingent Payment	(80)	164	50
(Gain) Loss on Divestiture of Assets	(81)	(2)	795
Other (Income) Loss, Net	40	9	13
Rolling Twelve Month Basis
Disclosure Of Objectives Policies And Processes For Managing Capital [Line Items]
Short-Term Borrowings	121
Current Portion of Long-Term Debt			682
Long-Term Debt	7,441	6,699	8,482
Less: Cash and Cash Equivalents	(378)	(186)	(781)
Net Debt	7,184	6,513	8,383
Net Earnings (Loss)	(2,379)	2,194	(2,669)
Add (Deduct):
Finance Costs	536	511	628
Interest Income	(9)	(12)	(19)
Income Tax Expense (Recovery)	(851)	(797)	(920)
Depreciation, Depletion and Amortization	3,464	2,249	2,131
Exploration Expense	91	82	2,123
Unrealized (Gain) Loss on Risk Management	56	149	(1,249)
Foreign Exchange (Gain) Loss, Net	(181)	(404)	854
Re-measurement of Contingent Payment	(80)	164	50
(Gain) Loss on Discontinuance			(301)
(Gain) Loss on Divestiture of Assets	(81)	(2)	795
Other (Income) Loss, Net	40	9	13
Adjusted EBITDA	$ 606	$ 4,143	$ 1,436
Net Debt to Adjusted EBITDA	11.9	1.6	5.8

Long-term Debt and Capital St_8

Long-term Debt and Capital Structure - Summary of Net Debt to Capitalization (Detail) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Disclosure Of Objectives Policies And Processes For Managing Capital [Abstract]
Net Debt	$ 7,184	$ 6,513	$ 8,383
Shareholders’ Equity	16,707	19,201	17,468	$ 19,981
Debt and Shareholders' Equity, Net	$ 23,891	$ 25,714	$ 25,851
Net Debt to Capitalization	30.00%	25.00%	32.00%

Lease Liabilities - Summary of

Lease Liabilities - Summary of Lease Liabilities (Details) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Lease Liabilities [Abstract]
Lease Liabilities, Beginning of Year	$ 1,916	$ 1,494
Additions	49	590
Interest Expense	87	82
Lease Payments	(284)	(232)
Terminations	(1)	(11)
Modifications	(2)
Re-measurement	(2)	15
Exchange Rate Movements and Other	(6)	(22)
Lease Liabilities, End of Year	1,757	1,916
Less: Current Portion	184	196
Long-Term Portion	$ 1,573	$ 1,720

Lease Liabilities - Summary o_2

Lease Liabilities - Summary of Lease Liabilities Depending on Duration of Lease Term (Details) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Lease Liabilities [Abstract]
Variable Lease Payments	$ 16	$ 19
Short-Term Lease Payments	$ 6	$ 13

Contingent Payment - Summary of

Contingent Payment - Summary of Contingent Payment (Detail) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disclosure Of Contingent Liabilities In Business Combination [Abstract]
Contingent Payment, Beginning of Year	$ 143	$ 132
Re-measurement	(80)	164
Liabilities Settled or Payable		(153)
Contingent Payment, End of Year	63	143
Less: Current Portion	36	79
Long-Term Portion	$ 27	$ 64

Contingent Payment - Additional

Contingent Payment - Additional Information (Detail)	May 17, 2017CAD ($)$ / bbl	Dec. 31, 2020CAD ($)$ / bbl	Dec. 31, 2019CAD ($)
Disclosure Of Contingent Liabilities In Business Combination [Line Items]
Contingent payable			$ 153,000,000
ConocoPhillips [Member]
Disclosure Of Contingent Liabilities In Business Combination [Line Items]
Contingent payment description		In connection with the acquisition (the “Acquisition in 2017”) from ConocoPhillips Company and certain of its subsidiaries (collectively, “ConocoPhillips”), Cenovus agreed to make quarterly payments to ConocoPhillips during the five years subsequent to May 17, 2017 for quarters in which the average WCS crude oil price exceeds $52.00 per barrel during the quarter. The quarterly payment will be $6 million for each dollar that the WCS price exceeds $52.00 per barrel. The calculation includes an adjustment mechanism related to certain significant production outages at Foster Creek and Christina Lake, which may reduce the amount of a contingent payment. There are no maximum payment terms.
Contingent payments period		5 years
Average crude oil price per barrel for contingent payment | $ / bbl		52
Quarterly contingent payment	$ 6,000,000
Contingent payable		$ 0	$ 14,000,000
ConocoPhillips [Member] | Top of Range [Member]
Disclosure Of Contingent Liabilities In Business Combination [Line Items]
Average crude oil price per barrel for contingent payment | $ / bbl	52

Decommissioning Liabilities - S

Decommissioning Liabilities - Summary of Decommissioning Provision (Detail) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Provision For Decommissioning Restoration And Rehabilitation Costs [Abstract]
Beginning balance	$ 1,235	$ 875
Liabilities Incurred	14	3
Liabilities Settled	(42)	(52)
Liabilities Disposed	(2)	(8)
Change in Estimated Future Cash Flows	13	21
Change in Discount Rate	(28)	339
Unwinding of Discount on Decommissioning Liabilities (Note 6)	57	58
Foreign Currency Translation	1	(1)
Ending balance	$ 1,248	$ 1,235

Decommissioning Liabilities - A

Decommissioning Liabilities - Additional Information (Detail) - CAD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disclosure Of Other Provisions [Line Items]
Estimated future cash flows required to settle the obligation	$ 4,953,000,000	$ 5,173,000,000
Credit-adjusted risk-free rate	5.00%	4.90%
Inflation Rate	2.00%	2.00%
Bottom of Range [Member]
Disclosure Of Other Provisions [Line Items]
Settlement Of Decommissioning Liabilities	$ 40,000,000
Top of Range [Member]
Disclosure Of Other Provisions [Line Items]
Settlement Of Decommissioning Liabilities	$ 45,000,000

Decommissioning Liabilities -_2

Decommissioning Liabilities - Summary of Changes to the Credit-Adjusted Risk-Free Rate or the Inflation Rate Impact on the Decommissioning Liabilities (Detail) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
One percent increase [member]
Disclosure Of Other Provisions [Line Items]
Credit-Adjusted Risk-Free Rate	$ (228)	$ (236)
Inflation Rate	321	340
One percent decrease [member]
Disclosure Of Other Provisions [Line Items]
Credit-Adjusted Risk-Free Rate	313	332
Inflation Rate	$ (235)	$ (243)

Other Liabilities - Summary of

Other Liabilities - Summary of Other Liabilities (Detail) - CAD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Miscellaneous Noncurrent Liabilities [Abstract]
Employee Long-Term Incentives	$ 33	$ 103
Pension and Other Post-Employment Benefit Plan (Note 29)	91	73
Onerous Contract Provisions	39	46
Other	18	19
Other Liabilities	$ 181	$ 241

Pensions and Other Post-Emplo_3

Pensions and Other Post-Employment Benefits - Additional Information (Detail) $ in Millions	Dec. 31, 2020Age	Dec. 31, 2020CAD ($)Age
Bottom of Range [Member]
Disclosure Of Defined Benefit Plans [Line Items]
Defined benefit plan, equity securities assets allocation percentage	25.00%
Defined benefit plan, fixed income assets allocation percentage	25.00%
Defined benefit plan, real estate assets allocation percentage	0.00%
Defined benefit plan, listed infrastructure assets allocation percentage	0.00%
Defined benefit plan, emerging market debts assets allocation percentage	0.00%
Defined benefit plan, cash and cash equivalents assets allocation percentage	0.00%
Top of Range [Member]
Disclosure Of Defined Benefit Plans [Line Items]
Defined benefit plan, equity securities assets allocation percentage	70.00%
Defined benefit plan, fixed income assets allocation percentage	35.00%
Defined benefit plan, real estate assets allocation percentage	15.00%
Defined benefit plan, listed infrastructure assets allocation percentage	10.00%
Defined benefit plan, emerging market debts assets allocation percentage	10.00%
Defined benefit plan, cash and cash equivalents assets allocation percentage	10.00%
OPEB [Member]
Disclosure Of Defined Benefit Plans [Line Items]
Maximum age for retired employees eligible for health care dental and life insurance benefits | Age	65	65
Weighted average duration		13 years 3 months 18 days
Pension Benefits [Member]
Disclosure Of Defined Benefit Plans [Line Items]
Weighted average duration		17 years 4 months 24 days
Percentage of employees contribution under pension plan		4.00%
Employer contribution | $		$ 10

Pensions and Other Post-Emplo_4

Pensions and Other Post-Employment Benefits - Summary of Defined Benefit and OPEB Plan Obligation and Funded Status (Detail) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Pension Benefits [Member]
Disclosure Of Net Defined Benefit Liability Asset [Line Items]
Current Service Costs	$ 13	$ 11	$ 13
Interest Income (Costs)	(3)	(3)	(3)
Re-measurements:
(Gains) Losses From Experience Adjustments	1	(4)
(Gains) Losses From Changes in Financial Assumptions	15	12
Return on Plan Assets (Excluding Interest Income)	5	15	(7)
Pension and OPEB (Liability)	(71)	(51)
Pension Benefits [Member] | Present value of defined benefit obligation [Member]
Disclosure Of Net Defined Benefit Liability Asset [Line Items]
Defined Benefit Obligation, Beginning of Year	158	167
Current Service Costs	13	11
Interest Income (Costs)	5	6
Benefits Paid	(6)	(36)
Plan Participant Contributions	2	2
Re-measurements:
(Gains) Losses From Experience Adjustments	1	(4)
(Gains) Losses From Changes in Financial Assumptions	15	12
Defined Benefit Obligation, End of Year	188	158	167
Pension Benefits [Member] | Plan assets [Member]
Disclosure Of Net Defined Benefit Liability Asset [Line Items]
Fair Value of Plan Assets, Beginning of Year	107	113
Interest Income (Costs)	2	3
Benefits Paid	(5)	(35)
Employer Contributions	6	9
Plan Participant Contributions	2	2
Re-measurements:
Return on Plan Assets (Excluding Interest Income)	5	15
Fair Value of Plan Assets, End of Year	117	107	113
OPEB [Member]
Disclosure Of Net Defined Benefit Liability Asset [Line Items]
Current Service Costs	1	1	1
Interest Income (Costs)		(1)	(1)
Re-measurements:
(Gains) Losses From Experience Adjustments	(2)
(Gains) Losses From Changes in Financial Assumptions	1	1	(1)
Pension and OPEB (Liability)	(20)	(22)
OPEB [Member] | Present value of defined benefit obligation [Member]
Disclosure Of Net Defined Benefit Liability Asset [Line Items]
Defined Benefit Obligation, Beginning of Year	22	21
Current Service Costs	1	1
Interest Income (Costs)		1
Benefits Paid	(2)	(2)
Re-measurements:
(Gains) Losses From Experience Adjustments	(2)
(Gains) Losses From Changes in Financial Assumptions	1	1
Defined Benefit Obligation, End of Year	$ 20	$ 22	$ 21

Pensions and Other Post-Emplo_5

Pensions and Other Post-Employment Benefits - Summary of Pension and OPEB Costs (Detail) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Re-measurements:
Defined Benefit Plan Cost (Recovery)	$ 33	$ 29	$ 30
Pension Benefits [Member]
Disclosure Of Defined Benefit Plans [Line Items]
Current Service Costs	13	11	13
Past Service Costs – Curtailments			(2)
Net Interest Costs	3	3	3
Re-measurements:
Return on Plan Assets (Excluding Interest Income)	(5)	(15)	7
(Gains) Losses From Experience Adjustments	1	(4)
(Gains) Losses From Changes in Financial Assumptions	15	12
Defined Benefit Plan Cost (Recovery)	27	7	21
Defined Contribution Plan Cost	22	21	22
Total Plan Cost	49	28	43
OPEB [Member]
Disclosure Of Defined Benefit Plans [Line Items]
Current Service Costs	1	1	1
Net Interest Costs		1	1
Re-measurements:
(Gains) Losses From Experience Adjustments	(2)
(Gains) Losses From Changes in Financial Assumptions	$ 1	1	(1)
Defined Benefit Plan Cost (Recovery)		3	1
Total Plan Cost		$ 3	$ 1

Pensions and Other Post-Emplo_6

Pensions and Other Post-Employment Benefits - Summary of Fair Value of the Plan Assets (Detail) - CAD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Disclosure Of Fair Value Of Plan Assets [Abstract]
Equity Funds	$ 58	$ 59
Fixed Income Funds	35	35
Real Estate Funds	6
Listed Infrastructure Funds	8	9
Emerging Market Debt Funds	7
Non-Invested Assets	1	2
Cash and Cash Equivalents	2	2
Total fair value	$ 117	$ 107

Pensions and Other Post-Emplo_7

Pensions and Other Post-Employment Benefits - Summary of Principal Weighted Average Actuarial Assumptions Used to Determine Benefit Obligations and Expenses (Detail) - yr	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Pension Benefits [Member]
Disclosure Of Actuarial Assumptions [Line Items]
Discount Rate	2.50%	3.00%	3.50%
Future Salary Growth Rate	3.97%	3.94%	3.88%
Average Longevity (years)	88.3	88.2	88.2
OPEB [Member]
Disclosure Of Actuarial Assumptions [Line Items]
Discount Rate	2.50%	3.00%	3.50%
Future Salary Growth Rate	4.94%	5.08%	5.08%
Average Longevity (years)	88.2	88.2	88.1
Health Care Cost Trend Rate	6.00%	6.00%	6.00%

Pensions and Other Post-Emplo_8

Pensions and Other Post-Employment Benefits - Sensitivity of Defined Benefit and OPEB Obligation to Changes in Relevant Actuarial Assumptions (Detail) - CAD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Discount Rate [Member]
Disclosure Of Sensitivity Analysis For Actuarial Assumptions [Line Items]
Increase	$ (31)	$ (25)
Decrease	$ 40	$ 32
Sensitivity Range - One percent change	1.00%	1.00%
Future Salary Growth Rate [Member]
Disclosure Of Sensitivity Analysis For Actuarial Assumptions [Line Items]
Increase	$ 4	$ 3
Decrease	$ (4)	$ (3)
Sensitivity Range - One percent change	1.00%	1.00%
Health Care Cost Trend Rate [Member]
Disclosure Of Sensitivity Analysis For Actuarial Assumptions [Line Items]
Increase	$ 1	$ 1
Decrease	$ (1)	$ (1)
Sensitivity Range - One percent change	1.00%	1.00%
One Year Change in Assumed Life Expectancy [Member]
Disclosure Of Sensitivity Analysis For Actuarial Assumptions [Line Items]
Increase	$ 4	$ 3
Decrease	$ (4)	$ (3)
Sensitivity Range - One percent change	1.00%	1.00%

Share Capital - Additional Info

Share Capital - Additional Information (Detail) - shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure of classes of share capital [Line Items]
Maximum percentage of preferred stock upon issuance or outstanding of common stock	20.00%
Number of common shares authorized	unlimited
Shares outstanding	1,228,870,000	1,228,828,000	1,228,790,000
Preferred Shares [Member]
Disclosure of classes of share capital [Line Items]
Shares outstanding	0	0
Stock Option Plan [Member]
Disclosure of classes of share capital [Line Items]
Shares available for future issuance	27,000,000	26,000,000

Share Capital - Summary of Shar

Share Capital - Summary of Share Capital (Detail) - CAD ($) shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disclosure Of Classes Of Share Capital [Abstract]
Outstanding, Beginning of Year	1,228,828	1,228,790
Common Shares Issued Under Stock Option Plan (Note 32)	42	38
Outstanding, End of Year	1,228,870	1,228,828
Outstanding, Beginning of Year	$ 11,040	$ 11,040
Common Shares Issued Under Stock Option Plan (Note 32)	0	0
Outstanding, End of Year	$ 11,040	$ 11,040

Share Capital - Schedule of Pai

Share Capital - Schedule of Paid in Surplus Includes Stock Based Compensation Expense (Detail) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disclosure of reserves within equity [line items]
Beginning Balance	$ 4,377	$ 4,367
Stock-Based Compensation Expense	14	10
Ending Balance	4,391	4,377
Pre-Arrangement Earnings [member]
Disclosure of reserves within equity [line items]
Beginning Balance	4,086	4,086
Stock-Based Compensation Expense	0	0
Ending Balance	4,086	4,086
Stock-Based Compensation [member]
Disclosure of reserves within equity [line items]
Beginning Balance	291	281
Stock-Based Compensation Expense	14	10
Ending Balance	$ 305	$ 291

Accumulated Other Comprehensi_3

Accumulated Other Comprehensive Income (Loss) - Schedule of Accumulated Other Comprehensive Income (Loss) (Detail) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disclosure of accumulated other comprehensive income loss [line items]
Beginning Balance	$ 827	$ 1,038
Other Comprehensive Income (Loss), Before Tax	(54)	(208)
Income Tax	2	(3)
Ending Balance	775	827
Defined Benefit Pension Plan [Member]
Disclosure of accumulated other comprehensive income loss [line items]
Beginning Balance	(2)	(7)
Other Comprehensive Income (Loss), Before Tax	(10)	6
Income Tax	2	(1)
Ending Balance	(10)	(2)
Private Equity Instruments [Member]
Disclosure of accumulated other comprehensive income loss [line items]
Beginning Balance	27	15
Other Comprehensive Income (Loss), Before Tax		14
Income Tax		(2)
Ending Balance	27	27
Foreign Currency Translation Adjustment [Member]
Disclosure of accumulated other comprehensive income loss [line items]
Beginning Balance	802	1,030
Other Comprehensive Income (Loss), Before Tax	(44)	(228)
Ending Balance	$ 758	$ 802

Stock-Based Compensation Plan_2

Stock-Based Compensation Plans - Additional Information (Detail) shares in Thousands	Jan. 01, 2021shares	Dec. 31, 2020CAD ($)sharesPlan	Dec. 31, 2019CAD ($)
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Liabilities from share based payment		$ 130,000,000	$ 60,000,000
NSRs [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Options expiration term		7 years
Weighted average unit fair value of granted		$ 2.27
NSRs [Member] | Events After Reporting [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Additional NSR vested and exercisable | shares	2,738
PSUs [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Vesting period		3 years
Liabilities from share based payment		$ 65,000,000	53,000,000
Number of shares vested | shares		7,055
Weighted average trading days		30 days
Intrinsic value of vested		$ 51,000,000	0
PSUs [Member] | Bottom of Range [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Percentage of units vesting		0.00%
PSUs [Member] | Top of Range [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Percentage of units vesting		200.00%
RSUs [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Vesting period		3 years
Liabilities from share based payment		$ 61,000,000	63,000,000
Number of shares vested | shares		8,237
Weighted average trading days		30 days
Intrinsic value of vested		$ 60,000,000	0
DSUs [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Liabilities from share based payment		$ 10,000,000	$ 16,000,000
Number of Deferred Share Unit Plans | Plan		2
DSUs Option One [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Percentage of annual bonus award to convert into DSUs		0.00%
DSUs Option Two [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Percentage of annual bonus award to convert into DSUs		25.00%
DSUs Option Three [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Percentage of annual bonus award to convert into DSUs		50.00%
Later than one year [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Percentage of options exercisable		30.00%
Later than two years and not later than three years [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Percentage of options exercisable		30.00%

Stock-Based Compensation Plan_3

Stock-Based Compensation Plans - Summary of Assumptions Used to Determine Fair Value of Options Granted (Detail) - NSRs [Member]	12 Months Ended
	Dec. 31, 2020yr
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Risk-Free Interest Rate	1.19%
Expected Dividend Yield	1.77%
Expected Volatility	29.74%
Expected Life	5

Stock-Based Compensation Plan_4

Stock-Based Compensation Plans - Summary of Stock Option Activity and Related Information (Detail) shares in Thousands	12 Months Ended
	Dec. 31, 2020shares$ / shares
NSRs [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Number of Share Options Outstanding, Beginning of Year	31,528
Number of Share Options, Granted	5,783
Number of Share Options, Exercised	(42)
Number of Share Options, Forfeited	(416)
Number of Share Options, Expired	(6,256)
Number of Share Options Outstanding, End of Year	30,597
Weighted Average Exercise Price, Outstanding, Beginning of Year | $ / shares	$ 22.61
Weighted Average Exercise Price, Granted | $ / shares	11.73
Weighted Average Exercise Price, Exercised | $ / shares	9.48
Weighted Average Exercise Price, Forfeited | $ / shares	23.52
Weighted Average Exercise Price, Expired | $ / shares	32.60
Weighted Average Exercise Price, Outstanding, End of Year | $ / shares	$ 18.52
PSUs [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Number of Share Units, Outstanding, Beginning of Year	6,912
Number of Share Units, Granted	3,846
Number of Share Units, Vested and Paid Out	(1,223)
Number of Share Units, Cancelled	(449)
Number of Share Units, Units in Lieu of Dividends	198
Number of Share Units, Outstanding, End of Year	9,284
RSUs [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Number of Share Units, Outstanding, Beginning of Year	8,372
Number of Share Units, Granted	2,686
Number of Share Units, Vested and Paid Out	(2,606)
Number of Share Units, Cancelled	(234)
Number of Share Units, Units in Lieu of Dividends	212
Number of Share Units, Outstanding, End of Year	8,430
DSUs [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Number of Share Units, Outstanding, Beginning of Year	1,237
Number of Share Units, Granted	30
Number of Share Units, Units in Lieu of Dividends	33
Number of Share Units, Redeemed	(255)
Number of Share Units, Outstanding, End of Year	1,333
DSUs [Member] | Director [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Number of Share Units, Granted	288

Stock-Based Compensation Plan_5

Stock-Based Compensation Plans - Summary of Options Outstanding and Exercisable by Range of Exercise Price (Detail) - NSRs [Member] shares in Thousands	12 Months Ended
	Dec. 31, 2020shares$ / shares	Dec. 31, 2019shares$ / shares
Disclosure of range of exercise prices of outstanding share options [Line Items]
Outstanding Number | shares	30,597	31,528
Outstanding Weighted Average Remaining Contractual Life	2 years 10 months 24 days
Outstanding Weighted Average Exercise Price | $ / shares	$ 18.52	$ 22.61
Exercisable Number | shares	20,665
Exercisable Weighted Average Exercise Price | $ / shares	$ 21.94
5.00 to 9.99 [Member]
Disclosure of range of exercise prices of outstanding share options [Line Items]
Outstanding Number | shares	2,796
Outstanding Weighted Average Remaining Contractual Life	4 years 2 months 12 days
Outstanding Weighted Average Exercise Price | $ / shares	$ 9.48
Exercisable Number | shares	1,596
Exercisable Weighted Average Exercise Price | $ / shares	$ 9.48
10.00 to 14.99 [Member]
Disclosure of range of exercise prices of outstanding share options [Line Items]
Outstanding Number | shares	12,921
Outstanding Weighted Average Remaining Contractual Life	5 years 2 months 12 days
Outstanding Weighted Average Exercise Price | $ / shares	$ 12.27
Exercisable Number | shares	4,189
Exercisable Weighted Average Exercise Price | $ / shares	$ 13.53
15.00 to 19.99 [Member]
Disclosure of range of exercise prices of outstanding share options [Line Items]
Outstanding Number | shares	2,691
Outstanding Weighted Average Remaining Contractual Life	2 years 3 months 18 days
Outstanding Weighted Average Exercise Price | $ / shares	$ 19.47
Exercisable Number | shares	2,691
Exercisable Weighted Average Exercise Price | $ / shares	$ 19.47
20.00 to 24.99 [Member]
Disclosure of range of exercise prices of outstanding share options [Line Items]
Outstanding Number | shares	3,078
Outstanding Weighted Average Remaining Contractual Life	1 year 1 month 6 days
Outstanding Weighted Average Exercise Price | $ / shares	$ 22.26
Exercisable Number | shares	3,078
Exercisable Weighted Average Exercise Price | $ / shares	$ 22.26
25.00 to 29.99 [Member]
Disclosure of range of exercise prices of outstanding share options [Line Items]
Outstanding Number | shares	8,540
Outstanding Weighted Average Remaining Contractual Life	1 month 6 days
Outstanding Weighted Average Exercise Price | $ / shares	$ 28.37
Exercisable Number | shares	8,540
Exercisable Weighted Average Exercise Price | $ / shares	$ 28.37
30.00 to 34.99 [Member]
Disclosure of range of exercise prices of outstanding share options [Line Items]
Outstanding Number | shares	571
Outstanding Weighted Average Remaining Contractual Life	6 months
Outstanding Weighted Average Exercise Price | $ / shares	$ 32.27
Exercisable Number | shares	571
Exercisable Weighted Average Exercise Price | $ / shares	$ 32.27

Stock-Based Compensation Plan_6

Stock-Based Compensation Plans - Summary of Options Outstanding and Exercisable by Range of Exercise Price (Parenthetical) (Detail) - NSRs [Member]	Dec. 31, 2020$ / shares
Bottom of Range [Member] | 5.00 to 9.99 [Member]
Disclosure of range of exercise prices of outstanding share options [Line Items]
Exercise price of warrants	$ 5
Bottom of Range [Member] | 10.00 to 14.99 [Member]
Disclosure of range of exercise prices of outstanding share options [Line Items]
Exercise price of warrants	10
Bottom of Range [Member] | 15.00 to 19.99 [Member]
Disclosure of range of exercise prices of outstanding share options [Line Items]
Exercise price of warrants	15
Bottom of Range [Member] | 20.00 to 24.99 [Member]
Disclosure of range of exercise prices of outstanding share options [Line Items]
Exercise price of warrants	20
Bottom of Range [Member] | 25.00 to 29.99 [Member]
Disclosure of range of exercise prices of outstanding share options [Line Items]
Exercise price of warrants	25
Bottom of Range [Member] | 30.00 to 34.99 [Member]
Disclosure of range of exercise prices of outstanding share options [Line Items]
Exercise price of warrants	30
Top of Range [Member] | 5.00 to 9.99 [Member]
Disclosure of range of exercise prices of outstanding share options [Line Items]
Exercise price of warrants	9.99
Top of Range [Member] | 10.00 to 14.99 [Member]
Disclosure of range of exercise prices of outstanding share options [Line Items]
Exercise price of warrants	14.99
Top of Range [Member] | 15.00 to 19.99 [Member]
Disclosure of range of exercise prices of outstanding share options [Line Items]
Exercise price of warrants	19.99
Top of Range [Member] | 20.00 to 24.99 [Member]
Disclosure of range of exercise prices of outstanding share options [Line Items]
Exercise price of warrants	24.99
Top of Range [Member] | 25.00 to 29.99 [Member]
Disclosure of range of exercise prices of outstanding share options [Line Items]
Exercise price of warrants	29.99
Top of Range [Member] | 30.00 to 34.99 [Member]
Disclosure of range of exercise prices of outstanding share options [Line Items]
Exercise price of warrants	$ 34.99

Stock-Based Compensation Plan_7

Stock-Based Compensation Plans - Summary of Stock-Based Compensation (Detail) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Stock-Based Compensation Expense	$ 49	$ 67	$ 9
Stock-Based Compensation Costs Capitalized	16	20	4
Total Stock-Based Compensation	65	87	13
Net Settlement Rights [member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Stock-Based Compensation Expense	11	9	6
Performance Share Units [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Stock-Based Compensation Expense	19	15	(6)
Restricted Share Units [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Stock-Based Compensation Expense	23	34	$ 9
Deferred Share Units [Member]
Disclosure of terms and conditions of share-based payment arrangement [Line Items]
Stock-Based Compensation Expense	$ (4)	$ 9

Employee Salaries and Benefit_3

Employee Salaries and Benefit Expenses - Summary of Employee Salaries and Benefit Expenses (Detail) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Classes Of Employee Benefits Expense [Abstract]
Salaries, Bonuses and Other Short-Term Employee Benefits	$ 605	$ 567	$ 580
Post-Employment Benefits	33	29	30
Stock-Based Compensation Expense	49	67	9
Other Long-Term Incentive Benefits	(4)	31
Termination Benefits	9	6	63
Employee Salaries and Benefit Expenses	$ 692	$ 700	$ 682

Related Party Transactions - Su

Related Party Transactions - Summary of Key Management Compensation (Detail) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure Of Transactions Between Related Parties [Abstract]
Salaries, Director Fees and Short-Term Benefits	$ 21	$ 24	$ 20
Post-Employment Benefits	3	2	3
Stock-Based Compensation	15	22	5
Other Long-Term Incentive Benefits	1	1
Termination Benefits	6		9
Total compensation paid or payable	$ 46	$ 49	$ 37

Financial Instruments - Additio

Financial Instruments - Additional information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2020CAD ($)$ / bbl	Dec. 31, 2019CAD ($)	Dec. 31, 2018CAD ($)
Disclosure of detailed information about financial instruments [Line Items]
Long-term debt, carrying value	$ 7,441	$ 6,699
Cash collateral for risk management contracts price change	$ 59
Discounted Credit adjusted risk free rate	2.00%
Estimated fair value of contingent payment	$ 63	143	$ 132
WCS Forward Prices [Member]
Disclosure of detailed information about financial instruments [Line Items]
Average forward price for Western Canadian Select Crude Oil for the remaining term | $ / bbl	42.93
WTI Option Volatility [Member]
Disclosure of detailed information about financial instruments [Line Items]
Average implied volatility contingent payment percentage	35.60%
U.S. to Canadian Dollar Foreign Exchange Average Rate Volatility Contingent Payment [Member]
Disclosure of detailed information about financial instruments [Line Items]
Average implied volatility contingent payment percentage	6.80%
Level 2 of Fair Value Hierarchy [Member]
Disclosure of detailed information about financial instruments [Line Items]
Debt, fair value	$ 8,608	$ 7,610

Financial Instruments - Reconci

Financial Instruments - Reconciliation of Changes in the Fair Value of Available for Sale Financial Assets (Detail) - Level 3 of Fair Value Hierarchy [Member] - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disclosure of fair value measurement of assets [Line Items]
Fair Value, Beginning of Year	$ 52	$ 38
Change in Fair Value	0	14
Fair Value, End of Year	$ 52	$ 52

Financial Instruments - Summary

Financial Instruments - Summary of Urealized Risk Management Positions (Detail) - CAD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Disclosure Of Recurring Fair Value Measurement Of Assets And Liabilities [Line Items]
Risk Management Net	$ 53
Level 2 of Fair Value Hierarchy [Member]
Disclosure Of Recurring Fair Value Measurement Of Assets And Liabilities [Line Items]
Risk Management Net	(53)	$ 3
Level 2 of Fair Value Hierarchy [Member] | Commodity Price Risk [Member] | Crude Oil, Natural Gas and Condensate [Member]
Disclosure Of Recurring Fair Value Measurement Of Assets And Liabilities [Line Items]
Risk Management Asset	5	5
Risk Management Liability	58	2
Risk Management Net	$ (53)	$ 3

Financial Instruments - Summa_2

Financial Instruments - Summary of Fair Value Hierarchy for Risk Management Assets and Liabilities Carried at Fair Value (Detail) - CAD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Disclosure Of Levels Of Fair Value Hierarchy [Line Items]
Fair Value of Risk Management Assets and Liabilities	$ 53
Level 2 of Fair Value Hierarchy [Member]
Disclosure Of Levels Of Fair Value Hierarchy [Line Items]
Fair Value of Risk Management Assets and Liabilities	$ (53)	$ 3

Financial Instruments - Summa_3

Financial Instruments - Summary of Changes in the Fair Value of Cenovus's Risk Management Assets and Liabilities (Detail) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Reconciliation Of Changes In Fair Value Measurement Assets Liabilities [Abstract]
Fair Value of Contracts, Beginning of Year	$ 3	$ 160
Fair Value of Contracts Realized During the Year	252	7
Change in Fair Value of Contracts in Place at Beginning of Year and Contracts Entered Into During the Year	(308)	(156)
Unrealized Foreign Exchange Gain (Loss) on U.S. Dollar Contracts		(8)
Fair Value of Contracts, End of Year	$ (53)	$ 3

Financial Instruments - Summa_4

Financial Instruments - Summary of Offsetting Risk Management Positions (Detail) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disclosure Of Offsetting Of Financial Assets Liabilities [Abstract]
Gross Amount, Risk Management Asset	$ 70	$ 13
Amount Offset, Risk Management Asset	(65)	(8)
Net Amount per Consolidated Financial Statements, Risk Management Asset	5	5
Gross Amount, Risk Management Liabilities	123	10
Amount Offset, Risk Management Liabilities	(65)	(8)
Net Amount per Consolidated Financial Statements, Risk Management Liabilities	58	2
Gross Amount, Risk Management Net	(53)	3
Net Amount per Consolidated Financial Statements, Risk Management Net	$ (53)	$ 3

Financial Instruments - Summa_5

Financial Instruments - Summary of Changes in Inputs to Option Pricing Model, Resulted in Unrealized Gains (Losses) Impacting Earnings Before Income Tax (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2020CAD ($)	Dec. 31, 2019CAD ($)
WCS Forward Prices [Member]
Disclosure Of Sensitivity Of Fair Value Measurement To Changes In Unobservable Inputs Liabilities [Line Items]
Sensitivity Price Range	5	5
Increase in volatility	$ (41)	$ (129)
Decrease in volatility	$ 32	$ 80
WTI Option Volatility [Member]
Disclosure Of Sensitivity Of Fair Value Measurement To Changes In Unobservable Inputs Liabilities [Line Items]
Sensitivity Range	5.00%	5.00%
Increase in volatility	$ (18)	$ (45)
Decrease in volatility	$ 17	$ 42
Foreign Exchange Rate Option Volatility [Member]
Disclosure Of Sensitivity Of Fair Value Measurement To Changes In Unobservable Inputs Liabilities [Line Items]
Sensitivity Range	5.00%	5.00%
Increase in volatility	$ 7	$ 10
Decrease in volatility	$ (10)	$ (19)

Financial Instruments - Summa_6

Financial Instruments - Summary of Earnings Impact of (Gains) Losses from Risk Management Positions (Detail) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure Of Financial Instruments [Abstract]
Realized (Gain) Loss	$ 252	$ 7	$ 1,554
Unrealized (Gain) Loss	56	149	(1,249)
(Gain) Loss on Risk Management From Continuing Operations	$ 308	$ 156	$ 305

Risk Management - Additional In

Risk Management - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2020CAD ($)	Dec. 31, 2019CAD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Dec. 31, 2018CAD ($)	Dec. 31, 2017CAD ($)
Disclosure of Nature and Extent of Risks Arising from Financial Instruments [Line Items]
Total Debt Principal			$ 5,898	$ 4,998
Fair Value of Risk Management Assets and Liabilities	$ 53,000,000
1% increase/decrease in interest rate on floating rate debt	1,000,000	$ 3,000,000
Cash and cash equivalents	378,000,000	186,000,000			$ 781,000,000	$ 610,000,000
Available borrowing capacity	1,100,000,000
Uncommitted demand facilities	1,100,000,000
WRB [Member]
Disclosure of Nature and Extent of Risks Arising from Financial Instruments [Line Items]
Available borrowing capacity			55
Uncommitted demand facilities			55
Committed Credit Facility [Member]
Disclosure of Nature and Extent of Risks Arising from Financial Instruments [Line Items]
Cash and cash equivalents	$ 378,000,000
Top of Range [Member]
Disclosure of Nature and Extent of Risks Arising from Financial Instruments [Line Items]
Target debt to adjusted EBITDA ratio	2
Available borrowing capacity	$ 1,600,000,000
Uncommitted demand facilities	1,600,000,000
Amount of undrawn facilities for general purposes	$ 600,000,000
Interest rate risk [member]
Disclosure of Nature and Extent of Risks Arising from Financial Instruments [Line Items]
Changes in interest rate percentage	1.00%
Liquidity risk [member] | Committed Credit Facility [Member]
Disclosure of Nature and Extent of Risks Arising from Financial Instruments [Line Items]
Available borrowing capacity	$ 4,500,000,000
Uncommitted demand facilities	4,500,000,000
Liquidity risk [member] | Top of Range [Member] | Base Shelf Prospectus [Member]
Disclosure of Nature and Extent of Risks Arising from Financial Instruments [Line Items]
Available borrowing capacity			3,700
Uncommitted demand facilities			$ 3,700
Interest Rate, Foreign Exchange or Cross Currency Interest Rate Swap [Member]
Disclosure of Nature and Extent of Risks Arising from Financial Instruments [Line Items]
Total Debt Principal	0
Notional Amount of Interest Rate Swaps [member]
Disclosure of Nature and Extent of Risks Arising from Financial Instruments [Line Items]
Total Debt Principal		$ 0
Cross Currency Interest Rate Swap
Disclosure of Nature and Extent of Risks Arising from Financial Instruments [Line Items]
Total Debt Principal	$ 0
Trade receivables [member] | Credit risk [member] | Investment grade counterparties [member]
Disclosure of Nature and Extent of Risks Arising from Financial Instruments [Line Items]
Percent of accounts receivable held with investment grade counterparties	98.00%	97.00%	98.00%	97.00%
Number of days outstanding for accruals, joint operations, trade receivables and net investment in finance leases	60 days	60 days
Number of counterparties whose net settlement position individually accounts for more than 10 percent of the fair value of accruals, joint operations, trade receivables and net investment in finance lease	1	1	1	1
Average expected credit loss rate	0.50%	0.30%	0.50%	0.30%
Percentage of counterparties greater than 10 percent of accruals, joint operations, trade receivables and net investment in finance leases	10.00%

Risk Management - Net Fair Valu

Risk Management - Net Fair Value of Risk Management Positions (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2020CAD ($)$ / bblMMBbls	Dec. 31, 2019CAD ($)	Dec. 31, 2018CAD ($)
Disclosure of Derivative Financial Instruments [Line Items]
Fair Value Asset (Liability)	$ (53)	$ 3	$ 160
Fair value derivative financial instruments [Member]
Disclosure of Derivative Financial Instruments [Line Items]
Fair Value Asset (Liability)	$ (53)
Fair value derivative financial instruments [Member] | WTI Fixed - Sell [Member]
Disclosure of Derivative Financial Instruments [Line Items]
Notional Volumes | MMBbls	19.6
Terms	January 2021 - June 2022
Weighted Average Price | $ / bbl	43.99
Fair Value Asset (Liability)	$ (113)
Fair value derivative financial instruments [Member] | WTI Fixed - Buy [Member]
Disclosure of Derivative Financial Instruments [Line Items]
Notional Volumes | MMBbls	11.7
Terms	February 2021 - June 2022
Weighted Average Price | $ / bbl	44.55
Fair Value Asset (Liability)	$ 59
Fair value derivative financial instruments [Member] | Other Financial Positions [Member]
Disclosure of Derivative Financial Instruments [Line Items]
Fair Value Asset (Liability)	$ 1

Risk Management - Net Fair Va_2

Risk Management - Net Fair Value of Risk Management Positions (Parenthetical) (Detail) - Fair value derivative financial instruments [Member]	12 Months Ended
	Dec. 31, 2020
Bottom of Range [Member]
Disclosure of Derivative Financial Instruments [Line Items]
Average contract financial term	1 month
Top of Range [Member]
Disclosure of Derivative Financial Instruments [Line Items]
Average contract financial term	23 months

Risk Management - Impact of Flu

Risk Management - Impact of Fluctuating Commodity Prices and Interest Rates on Company'S Open Risk Management Positions (Detail) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Commodity Price Risk [Member] | Crude Oil Contracts [Member]
Disclosure of Nature and Extent of Risks Arising from Financial Instruments [Line Items]
Description of exposure to risk	Crude Oil Commodity Price	Crude Oil Commodity Price
Sensitivity Range	± US$5.00 per bbl Applied to WTI and Condensate Hedges	± US$5.00 per bbl Applied to WTI and Condensate Hedges
Increase	$ (44)	$ 3
Decrease	$ 44	$ (3)
Commodity Price Risk [Member] | Crude oil differential contracts [Member]
Disclosure of Nature and Extent of Risks Arising from Financial Instruments [Line Items]
Description of exposure to risk	Crude Oil Differential Price	Crude Oil Differential Price
Sensitivity Range	± US$2.50 per bbl Applied to Differential Hedges Tied to Production	± US$2.50 per bbl Applied to Differential Hedges Tied to Production
Increase	$ (2)	$ 5
Decrease	2	(5)
Currency risk [Member]
Disclosure of Nature and Extent of Risks Arising from Financial Instruments [Line Items]
$0.05 Increase in the Canadian per U.S. Dollar Foreign Exchange Rate	300	250
$0.05 Decrease in the Canadian per U.S. Dollar Foreign Exchange Rate	$ (300)	$ (250)

Risk Management - Undiscounted

Risk Management - Undiscounted Cash Outflows Relating to Financial Liabilities (Detail) - CAD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Accounts payable and accrued liabilities [member]
Disclosure of Maturity Analysis for Financial Liabilities [Line Items]
Financial instruments	$ 2,018	$ 2,229
Accounts payable and accrued liabilities [member] | Less Than 1 Year [Member]
Disclosure of Maturity Analysis for Financial Liabilities [Line Items]
Financial instruments	2,018	2,229
Short-term Borrowings [Member]
Disclosure of Maturity Analysis for Financial Liabilities [Line Items]
Financial instruments	121
Short-term Borrowings [Member] | Less Than 1 Year [Member]
Disclosure of Maturity Analysis for Financial Liabilities [Line Items]
Financial instruments	121
Long-term Borrowings [Member]
Disclosure of Maturity Analysis for Financial Liabilities [Line Items]
Financial instruments	12,943	12,473
Long-term Borrowings [Member] | Less Than 1 Year [Member]
Disclosure of Maturity Analysis for Financial Liabilities [Line Items]
Financial instruments	385	344
Long-term Borrowings [Member] | Years 2 and 3 [Member]
Disclosure of Maturity Analysis for Financial Liabilities [Line Items]
Financial instruments	1,965	1,338
Long-term Borrowings [Member] | Years 4 and 5 [Member]
Disclosure of Maturity Analysis for Financial Liabilities [Line Items]
Financial instruments	1,966	1,465
Long-term Borrowings [Member] | Thereafter [Member]
Disclosure of Maturity Analysis for Financial Liabilities [Line Items]
Financial instruments	8,627	9,326
Contingent Payment ([Member]
Disclosure of Maturity Analysis for Financial Liabilities [Line Items]
Financial instruments	64	148
Contingent Payment ([Member] | Less Than 1 Year [Member]
Disclosure of Maturity Analysis for Financial Liabilities [Line Items]
Financial instruments	36	79
Contingent Payment ([Member] | Years 2 and 3 [Member]
Disclosure of Maturity Analysis for Financial Liabilities [Line Items]
Financial instruments	28	69
Lease liabilities [member]
Disclosure of Maturity Analysis for Financial Liabilities [Line Items]
Financial instruments	2,476	2,697
Lease liabilities [member] | Less Than 1 Year [Member]
Disclosure of Maturity Analysis for Financial Liabilities [Line Items]
Financial instruments	254	277
Lease liabilities [member] | Years 2 and 3 [Member]
Disclosure of Maturity Analysis for Financial Liabilities [Line Items]
Financial instruments	445	466
Lease liabilities [member] | Years 4 and 5 [Member]
Disclosure of Maturity Analysis for Financial Liabilities [Line Items]
Financial instruments	365	410
Lease liabilities [member] | Thereafter [Member]
Disclosure of Maturity Analysis for Financial Liabilities [Line Items]
Financial instruments	$ 1,412	$ 1,544

Supplementary Cash Flow Infor_3

Supplementary Cash Flow Information - Summary of Supplementary Cash Flow Information (Detail) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure Of Supplementary Cash Flow Information [Abstract]
Interest Paid	$ 381	$ 457	$ 564
Interest Received	5	12	19
Income Taxes Paid	$ 18	$ 17	$ 116

Supplementary Cash Flow Infor_4

Supplementary Cash Flow Information - Summary of Reconciliation of Cash Flows from Financing Activities (Detail) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure Of Reconciliation Of Liabilities Arising From Financing Activities [Line Items]
Lease Liabilities, Beginning of Year	$ 1,916	$ 1,494
Changes From Financing Cash Flows:
Repayment of Long-Term Debt	(112)	(2,279)	$ (1,144)
Principal Repayment of Leases	(197)	(150)
Issuance of Long-Term Debt	1,326
Non-Cash Changes:
Additions	49	590
Lease Terminations	1	11
Lease Modifications	(2)
Other			(1)
Lease Liabilities, End of Year	1,757	1,916	1,494
Ending balance	121
Dividends Payable [Member]
Changes From Financing Cash Flows:
Dividends Paid	(77)	(260)	(245)
Non-Cash Changes:
Dividends Declared	77	260	245
Short-Term Borrowings [Member]
Changes From Financing Cash Flows:
Issuance (Repayment) of Short-Term Borrowings	117
Non-Cash Changes:
Foreign Exchange (Gain) Loss	4
Ending balance	121
Long-term Borrowings [Member]
Disclosure Of Reconciliation Of Liabilities Arising From Financing Activities [Line Items]
Beginning balance	6,699	9,164	9,513
Changes From Financing Cash Flows:
Repayment of Long-Term Debt	(112)	(2,279)	(1,144)
Net Issuance (Repayment) of Revolving Long-Term Debt	(220)	276	(20)
Issuance of Long-Term Debt	1,326
Non-Cash Changes:
Foreign Exchange (Gain) Loss	(231)	(399)	817
Finance Costs			(2)
Gain on Repurchase of Debt and Amortization of Debt Issuance Costs	(20)	(63)
Other	(1)
Ending balance	7,441	6,699	$ 9,164
Lease liabilities [member]
Disclosure Of Reconciliation Of Liabilities Arising From Financing Activities [Line Items]
Lease Liabilities, Beginning of Year	1,916
Changes From Financing Cash Flows:
Principal Repayment of Leases	(197)	(150)
Non-Cash Changes:
Foreign Exchange (Gain) Loss	(6)	(23)
Additions	49	590
Re-measurement of Lease Liabilities	(2)	15
Lease Terminations	(1)	(11)
Lease Modifications	(2)
Other		1
Lease Liabilities, End of Year	1,757	1,916
Lease liabilities [member] | IFRS 16 [Member] | Adjustments [Member]
Disclosure Of Reconciliation Of Liabilities Arising From Financing Activities [Line Items]
Lease Liabilities, Beginning of Year	$ 1,494
Non-Cash Changes:
Lease Liabilities, End of Year		$ 1,494

Commitments and Contingencies -

Commitments and Contingencies - Summary of Future Payments of Commitments (Detail) - CAD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Disclosure of commitments [Line Items]
Transportation and Storage	$ 21,397	$ 21,499
Real Estate	797	852
Capital Commitments	3
Other Long-Term Commitments	322	354
Total Payments	22,519	22,705
1 Year [member]
Disclosure of commitments [Line Items]
Transportation and Storage	1,014	1,005
Real Estate	34	35
Capital Commitments	1
Other Long-Term Commitments	104	104
Total Payments	1,153	1,144
2 Years [member]
Disclosure of commitments [Line Items]
Transportation and Storage	954	959
Real Estate	36	36
Capital Commitments	2
Other Long-Term Commitments	45	44
Total Payments	1,037	1,039
3 Years [Member]
Disclosure of commitments [Line Items]
Transportation and Storage	1,341	1,026
Real Estate	38	38
Other Long-Term Commitments	32	36
Total Payments	1,411	1,100
4 Years [member]
Disclosure of commitments [Line Items]
Transportation and Storage	1,444	1,456
Real Estate	41	39
Other Long-Term Commitments	32	34
Total Payments	1,517	1,529
5 Years [Member]
Disclosure of commitments [Line Items]
Transportation and Storage	1,107	1,381
Real Estate	44	42
Other Long-Term Commitments	24	28
Total Payments	1,175	1,451
Thereafter [Member]
Disclosure of commitments [Line Items]
Transportation and Storage	15,537	15,672
Real Estate	604	662
Other Long-Term Commitments	85	108
Total Payments	$ 16,226	$ 16,442

Commitments and Contingencies_2

Commitments and Contingencies - Summary of Future Payments of Commitments (Parenthetical) (Detail) - CAD ($) $ in Billions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disclosure of commitments [Line Items]
Transportation Commitment	$ 14	$ 13
Transportation Commitment Term	20 years	20 years
WRB [Member]
Disclosure of commitments [Line Items]
Percent of ownership in joint operations	50.00%	50.00%

Commitments and Contingencies_3

Commitments and Contingencies - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2020CAD ($)$ / bbl	Dec. 31, 2019CAD ($)	Dec. 31, 2018CAD ($)
Disclosure Of Commitments And Contingent Liabilities [Line Items]
Outstanding letters of credit	$ 441	$ 364
Decommissioning liabilities	1,248	1,235	$ 875
Estimated fair value of contingent payment	$ 63	143	$ 132
ConocoPhillips Company and Certain of its Subsidiaries [Member]
Disclosure Of Commitments And Contingent Liabilities [Line Items]
Quarterly payment tenure	5 years
Average crude oil price | $ / bbl	52
Estimated fair value of contingent payment	$ 63	$ 143
Storage Tank [Member]
Disclosure Of Commitments And Contingent Liabilities [Line Items]
Payments on future commitments not yet commenced	$ 31

Subsequent Event- Additional In

Subsequent Event- Additional Information (Details) $ / shares in Units, Warrant in Millions	Jan. 01, 2021CAD ($)sharesWarrant / sharesWarrant$ / shares	Dec. 31, 2020CAD ($)$ / shares	Dec. 31, 2019CAD ($)
Disclosure Of Nonadjusting Events After Reporting Period [Line Items]
Available borrowing capacity		$ 1,100,000,000
Transportation and Storage		21,397,000,000	$ 21,499,000,000
Transportation Commitment		$ 14,000,000,000	$ 13,000,000,000
Cenovus and Husky Merger [Member]
Disclosure Of Nonadjusting Events After Reporting Period [Line Items]
Number of shares issued | shares	0.7845
Number of warrants issued | Warrant / shares	0.0651
Closing share price reported on the TSX | $ / shares		$ 7.75
Fair value of warrants transferred	$ 216,000,000
Exercise price of warrants | $ / shares	$ 6.54
Number of common shares permitted for exchange of each stock option | shares	0.7845
Number of shares used for calculation of exercise price per share in option exchange | shares	0.7845
Fair value of replacement stock options	$ 9,000,000
Fair value of trade and other receivables acquired	1,100,000,000
Gross contractual amounts of trade and other receivables acquired	1,200,000,000
Best estimate at acquisition date of contractual cash flows not expected to be collected for acquired receivables	36,000,000
Acquisition related costs	29,000,000
Cash	735,000,000
Available borrowing capacity	3,700,000,000
Uncommitted demand facilities	508,000,000
Borrowing capacity from committed credit facilities	4,000,000,000
Borrowing capacity from uncommitted demand facilities	975,000,000
Amount of undrawn facilities for general purposes	850,000,000
Total commitments	18,700,000,000
Transportation and Storage	7,400,000,000
Transportation Commitment	$ 1,700,000,000
Common Share [Member] | Cenovus and Husky Merger [Member]
Disclosure Of Nonadjusting Events After Reporting Period [Line Items]
Number of instruments issued | shares	788,500,000
Fair value of shares transferred	$ 6,100,000,000
Common Share Purchase Warrants [Member] | Cenovus and Husky Merger [Member]
Disclosure Of Nonadjusting Events After Reporting Period [Line Items]
Number of instruments issued | Warrant	65.4
Common Share Warrants [Member] | Cenovus and Husky Merger [Member]
Disclosure Of Nonadjusting Events After Reporting Period [Line Items]
Fair value of warrants transferred	$ 216,000,000
Preferred Share [Member] | Cenovus and Husky Merger [Member]
Disclosure Of Nonadjusting Events After Reporting Period [Line Items]
Number of instruments issued | shares	36,000,000
Fair value of shares transferred	$ 519,000,000

Subsequent Event - Summary of D

Subsequent Event - Summary of Details of Consideration and Recognized Amounts of Assets Acquired and Liabilities Assumed (Details) - Cenovus and Husky Merger [Member] $ in Millions	Jan. 01, 2021CAD ($)
Disclosure Of Business Combinations [Line Items]
Share Purchase Warrants	$ 216
Replacement Stock Options	9
Non-Controlling Interest	11
Total Consideration and Non-Controlling Interest	6,866
Cash	735
Restricted Cash	164
Accounts Receivable and Accrued Revenues	1,272
Inventories	1,118
Property, Plant and Equipment, Intangible Assets and Deferred Income Tax Assets	15,227
Right-of-Use Assets	1,137
Long-Term Income Tax Receivable	202
Other Assets	200
Investments in Joint Ventures	457
Accounts Payable and Accrued Liabilities	(2,224)
Income Tax Payable	(59)
Current Portion of Long-Term Debt	(40)
Long-Term Debt	(6,602)
Lease Liabilities	(1,447)
Decommissioning Liabilities	(2,835)
Other Liabilities	(439)
Total Identifiable Net Assets	6,866
Common Share [Member]
Disclosure Of Business Combinations [Line Items]
Fair value of shares transferred	6,111
Preferred Share [Member]
Disclosure Of Business Combinations [Line Items]
Fair value of shares transferred	$ 519