Inventories - Narrative (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Public Utilities, Inventory [Line Items]
Impairment recognized due to lower than cost or market adjustments	$ 42	$ 0	$ 54
Commodity Inventories
Public Utilities, Inventory [Line Items]
Impairment recognized due to lower than cost or market adjustments	$ 7	$ 0	$ 76

Amount of loss from reductions in inventory due to subsequent measurement adjustments, including, but not limited to, physical deterioration, obsolescence, or changes in price levels.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 330
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=116847112&loc=d3e4542-108314

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