Fair Value of Financial Instruments - Schedule of Interest Rate Swaps Outstanding (Detail) - Interest Rate Swaps [Member] - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Aggregate Notional Amount	$ 554	$ 821
Gross Asset at Fair Value		1
Gross Liability at Fair Value	58	27
Gross losses	42	51	$ 12
Gross gains	$ 6	$ 11	$ 22

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 increase in the fair value of derivatives recognized in the income statement.

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Fair value of asset associated with 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.

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Amount of decrease in the fair value of derivatives recognized in the income statement.

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Nominal or face amount used to calculate payment on derivative.

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