Fair Value Measurements - Additional Information (Detail) $ in Millions	3 Months Ended	12 Months Ended
Dec. 31, 2018 USD ($) Vessel	Dec. 31, 2016 USD ($)	Dec. 31, 2017 USD ($)
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Aggregate carrying value of assets	$ 9,440		$ 3,223
Non-cash impairment charges		$ 32
Marine Assets [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Number of vessels \| Vessel	2
Aggregate carrying value of assets	$ 77	22
Estimated fair value of assets	19	10
Non-cash impairment charges	$ 58	12
Marine Assets [Member] \| NCSA [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Non-cash impairment charges		$ 11

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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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