Derivatives and Risk Management (Narrative) (Details) $ in Millions	Dec. 31, 2020 USD ($)
Not Designated as Hedging Instrument
Derivative [Line Items]
Impact of non-performance risk on fair value of the net derivative liability position	$ 1
Commodity Contract
Derivative [Line Items]
Derivative asset (liability)	$ (41)

Fair value of the assets less the liabilities of a derivative or group of derivatives.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=121572278&loc=d3e13433-108611

Name:	us-gaap_DerivativeFairValueOfDerivativeNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant