Period of time used as the basis for weather hedges entered into by the company.

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The aggregate fair value of additional assets that would be required to be posted as collateral for derivative instruments with credit-risk-related contingent features if the credit-risk-related contingent features were triggered at the end of the reporting period.

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The aggregate fair value of assets that are already posted, at the end of the reporting period, as collateral for derivative instruments with credit-risk-related contingent features.

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Fair value, before effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement.

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Amount of realized and unrealized gain (loss) of derivative instruments not designated or qualifying as hedging instruments.

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Nominal or face amount used to calculate payments on the derivative liability.

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The aggregate fair value amounts of derivative instruments that contain credit-risk-related contingent features that are in a net liability position at the end of the reporting period. For nonderivative instruments that are designated and qualify as hedging instruments, the fair value amounts are the carrying value of the nonderivative hedging instrument, including the adjustment for the foreign currency transaction gain (loss) on that instrument.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Derivative Instruments (Details) - USD ($) $ in Millions	3 Months Ended
Derivative Instruments (Details) - USD ($) $ in Millions	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Derivatives, Fair Value [Line Items]
Weather hedges term	10
Derivative Liability, Fair Value, Gross Liability	$ 943		$ 983
Gain (loss) on derivative instruments not designated as hedging instruments	26	$ 135
Credit Risk Related Contingent Features [Abstract]
Aggregate fair value of derivatives with credit-risk-related contingent features in a liability position	9		20
Fair value of collateral already posted	7		7
Additional collateral required to be posted if credit risk contingent features triggered (1)	2		3
Gains (Losses) in Other Income (Expense) [Member] \| IDS Derivative [Member]
Derivatives, Fair Value [Line Items]
Gain (loss) on derivative instruments not designated as hedging instruments	26	$ 135
Economic hedge (1) \| Interest Rate Contract [Member]
Derivatives, Fair Value [Line Items]
Economic hedge (1)	84		84
Not Designated as Hedging Instrument [Member] \| Current Liabilities [Member] \| IDS Derivative [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	927		953
Not Designated as Hedging Instrument [Member] \| Current Liabilities [Member] \| Energy Related Derivative [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	2		3
Not Designated as Hedging Instrument [Member] \| Other Noncurrent Liabilities [Member] \| Interest Rate Contract [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	9		20
Not Designated as Hedging Instrument [Member] \| Other Noncurrent Liabilities [Member] \| Energy Related Derivative [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	$ 5		$ 7