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.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
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Sum of the carrying amounts as of the balance sheet date of all liabilities that are recognized. Liabilities are probable future sacrifices of economic benefits arising from present obligations of an entity to transfer assets or provide services to other entities in the future.

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Unbilled amounts due for services rendered or to be rendered, actions taken or to be taken, or a promise to refrain from taking certain actions in accordance with the terms of a legally binding agreement between the entity and, at a minimum, one other party. An example would be amounts associated with contracts or programs where the recognized revenue for performance thereunder exceeds the amounts billed under the terms thereof as of the date of the balance sheet.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.3(c)(3))
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Revenues from contracts with customers - Narrative (Detail) - USD ($) $ in Millions	Mar. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Assets	$ 702,651		$ 702,095
Liabilities	351,599		350,141
ASC 606 [Member]
Disaggregation of Revenue [Line Items]
Assets		$ 3,382
Liabilities		3,453
Utilities and Energy [Member] \| Other Assets [Member]
Disaggregation of Revenue [Line Items]
Unbilled revenue	$ 582		$ 665
Sales of Fractional Aircraft Ownership Interests [Member] \| ASC 606 [Member]
Disaggregation of Revenue [Line Items]
Liabilities		3,500
Sales of Fractional Aircraft Ownership Interests [Member] \| ASC 606 [Member] \| Primarily Property, Plant and Equipment [Member]
Disaggregation of Revenue [Line Items]
Assets		$ 3,500