Business Segments - Additional Information (Detail) $ in Millions	3 Months Ended
Mar. 31, 2016 USD ($) Segment	Mar. 31, 2015 USD ($)
Segment Reporting Information [Line Items]
Reclassified corporate overhead cost	$ 50	$ 67
Number of reportable segments \| Segment	4
Stock-based compensation expense	$ 29	40
Voluntary Early Retirement Plan [Member]
Segment Reporting Information [Line Items]
Severance cost	45	58
Postretirement medical benefits	35	45
Stock-based compensation expense	5	$ 18
Accrued postretirement medical benefits	73
Other restructuring cost	$ 56

Prior period reclassified corporate overhead cost.

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Carrying value as of the balance sheet date of obligations, excluding pension and other postretirement benefits, incurred through that date and payable for perquisites provided to employees pertaining to services received from them.

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Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

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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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