Pension Plans and Other Postretirement Benefits Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2016	Mar. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Corresponding decrease in other comprehensive income related to the benefit obligation increase	$ 166	$ 0
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation increase for the period	146
Corresponding decrease in other comprehensive income related to the benefit obligation increase	146
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation increase for the period	26
Corresponding decrease in other comprehensive income related to the benefit obligation increase	26
Unfunded Plans Defined Benefit [Member] \| Pension Plan [Member] \| Employee Severance [Member]
Defined Benefit Plan Disclosure [Line Items]
Expected future employer contributions in 2016 related to the workforce reduction program	82
Expected future employer contributions in 2017 related to the workforce reduction program	$ 23

Amount of gain (loss) related to change in benefit obligation resulting from changes in actuarial assumptions, for example, but not limited to, interest, mortality, employee turnover, salary, and temporary deviation from the substantive plan.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Gain or Loss
-URI http://asc.fasb.org/extlink&oid=49168827

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (a)(4)
-URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920

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Amount of employer's best estimate of contributions expected to be paid to the plan in the current remaining fiscal period.

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Amount of employer's best estimate of contributions expected to be paid to the plan during the next fiscal year beginning after the date of the latest statement of financial position.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
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-URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920

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Amount before tax of (increase) decrease in the value of the projected benefit obligation related to a change in an actuarial assumption and increase (decrease) in the value of the plan assets resulting from experience different from that assumed, that has not been recognized in net periodic benefit (cost) credit.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
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-URI http://asc.fasb.org/extlink&oid=36458714&loc=d3e637-108580

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-Name Accounting Standards Codification
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-Section 45
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-URI http://asc.fasb.org/extlink&oid=36458714&loc=SL7669646-108580

Reference 3: http://www.xbrl.org/2003/role/presentationRef
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