Financial Risk Management Activities - Gross and Net Fair Values (Detail) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Derivatives Fair Value [Line Items]
Assets - Gross fair value of derivative contracts	$ 126	$ 484
Assets – Master netting arrangements	0	0
Assets - Net Fair Value of Derivative Contracts	126	484
Liabilities - Gross fair value of derivative contracts	(1)	(2)
Liabilities - Master netting arrangements	0	0
Liabilities - Net Fair Value of Derivative Contracts	(1)	(2)
Derivative Contracts Designated as Hedging Instruments
Derivatives Fair Value [Line Items]
Assets - Gross fair value of derivative contracts	126	484
Liabilities - Gross fair value of derivative contracts	0	(2)
Derivative Contracts Designated as Hedging Instruments \| Commodity \| Other Current Assets
Derivatives Fair Value [Line Items]
Assets - Gross fair value of derivative contracts	125	484
Liabilities - Gross fair value of derivative contracts	0	0
Derivative Contracts Designated as Hedging Instruments \| Interest Rate \| Other Assets (Noncurrent)
Derivatives Fair Value [Line Items]
Assets - Gross fair value of derivative contracts	1
Liabilities - Gross fair value of derivative contracts	0
Derivative Contracts Designated as Hedging Instruments \| Interest Rate \| Other Liabilities and Deferred Credits
Derivatives Fair Value [Line Items]
Assets - Gross fair value of derivative contracts		0
Liabilities - Gross fair value of derivative contracts		$ (2)
Derivative Contracts Not Designated as Hedging Instruments
Derivatives Fair Value [Line Items]
Assets - Gross fair value of derivative contracts	0
Liabilities - Gross fair value of derivative contracts	(1)
Derivative Contracts Not Designated as Hedging Instruments \| Foreign Exchange
Derivatives Fair Value [Line Items]
Assets - Gross fair value of derivative contracts	0
Liabilities - Gross fair value of derivative contracts	$ (1)

Fair value, before effects of master netting arrangements, of a financial asset or other 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 assets not subject to a master netting arrangement and elected not to be offset.

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Fair value of liability associated with financial asset or other 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.

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