Nominal number of units used to calculate payment on derivative.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5580258-113959

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=121590274&loc=SL5579245-113959

Name:	us-gaap_DerivativeNonmonetaryNotionalAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

Derivative and Financial Instruments - Commodity Notional (Details) - Commodity Contract [Member] - Bcfe Bcfe in Billions	Mar. 31, 2021	Dec. 31, 2020
Natural gas and power, Fixed price [Member] \| Long [Member]
Trading Activity, Gains and Losses, Net [Line Items]
Commodity derivatives - volumetric material net exposures	(17)
Natural gas and power, Fixed price [Member] \| Short [Member]
Trading Activity, Gains and Losses, Net [Line Items]
Commodity derivatives - volumetric material net exposures		(20)
Natural gas and power, Basis [Member] \| Short [Member]
Trading Activity, Gains and Losses, Net [Line Items]
Commodity derivatives - volumetric material net exposures	(12)	(10)