Investment in Cenovus Energy (Narrative) (Details) - Common Stock [Member] - Cenovus Energy Inc [Member] shares in Millions, $ in Millions	12 Months Ended
Dec. 31, 2021 USD ($) shares
Debt and Equity Securities, FV-NI [Line Items]
Equity securities, shares sold \| shares	117
Proceeds recognized from sale of equity securities	$ 1,140
Proceeds received from sale of equity securities	$ 1,180

Amount of cash inflow from sale of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI), classified as investing activity.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 19
-URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3444-108585

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 321
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=123583714&loc=SL75117360-209713

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration