Fair Value Measurements - Additional Information (Detail) $ in Millions	3 Months Ended
Sep. 30, 2019 USD ($) SupportSystem	Dec. 31, 2018 USD ($) Vessel	Dec. 31, 2019 USD ($)
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Aggregate carrying value of assets		$ 9,440	$ 8,737
Marine Assets [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Number of offshore diving operations saturation support systems \| SupportSystem	2
Aggregate carrying value of assets	$ 26	77
Estimated fair value of assets	8	19
Non-cash impairment charges	$ 18	$ 58
Number of vessels \| Vessel		2

Number of offshore diving operations saturation support systems.

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Number of vessels.

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- Definition

Amount of write-down of assets recognized in the income statement. Includes, but is not limited to, losses from tangible assets, intangible assets and goodwill.

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Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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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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