Post-Employment and Other Long-Term Employees Benefits - Reconciliation for Plan Assets Measured at Fair Value Using Unobservable Inputs (Level 3) (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value at beginning of year	$ 448
Foreign currency translation adjustment	(1)
Plan assets at fair value at end of year	480
Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets at fair value at beginning of year	109	120
Contributions (employer and employee)	14	15
Actual return on plan assets	6
Benefits paid	(3)	(2)
Assets sold during the year	(2)
Settlements	(11)	(23)
ST-Ericsson deconsolidation		(4)
Foreign currency translation adjustment	(11)	3
Plan assets at fair value at end of year	$ 102	$ 109

Post-Employment and Other Long-Term Employees Benefits - Reconciliation for Plan Assets Measured at Fair Value Using Unobservable Inputs (Level 3) (Detail) (USD $)
In Millions, unless otherwise specified

12 Months Ended

Dec. 31, 2014

Dec. 31, 2013

Defined Benefit Plan Disclosure [Line Items]

Plan assets at fair value at beginning of year

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Foreign currency translation adjustment

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Plan assets at fair value at end of year

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Fair Value, Inputs, Level 3 [Member]

Defined Benefit Plan Disclosure [Line Items]

Plan assets at fair value at beginning of year

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Contributions (employer and employee)

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Actual return on plan assets

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Benefits paid

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Assets sold during the year

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Settlements

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ST-Ericsson deconsolidation

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Foreign currency translation adjustment

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Plan assets at fair value at end of year

$ 102us-gaap_DefinedBenefitPlanFairValueOfPlanAssets
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$ 109us-gaap_DefinedBenefitPlanFairValueOfPlanAssets
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- Definition

The increase in the fair value of plan assets from contributions made by the employer and employee.

+ References

No definition available.

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- Definition

The difference between fair value of plan assets at the end of the period and the fair value at the beginning of the period, adjusted for contributions and payments of benefits during the period, and after adjusting for taxes and other expenses, as applicable.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Actual Return on Plan Assets (Component of Net Periodic Postretirement Benefit Cost)

-URI http://asc.fasb.org/extlink&oid=6504192

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (b)(1)

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-Publisher FASB

-Name Accounting Standards Codification

-Glossary Actual Return on Plan Assets (Component of Net Periodic Pension Cost)

-URI http://asc.fasb.org/extlink&oid=6504226

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- Definition

Actual return on plan assets, separately identifying the amount related to assets sold during the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (d)(iv)(02)(A)

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- Definition

The amount of payments made for which participants are entitled under a pension plan, including pension benefits, death benefits, and benefits due on termination of employment. Also includes payments made under a postretirement benefit plan, including prescription drug benefits, health care benefits, life insurance benefits, and legal, educational and advisory services. This item represents a periodic decrease to the plan obligations and a decrease to plan assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Postretirement Benefits

-URI http://asc.fasb.org/extlink&oid=6521376

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 60

-Section 50

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=6414203&loc=d3e39716-114964

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 30

-Glossary Benefits

-URI http://asc.fasb.org/extlink&oid=6506267

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 60

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-Publisher FASB

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-Topic 715

-SubTopic 20

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-Subparagraph (a)(6)

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-Topic 715

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-Paragraph 1

-Subparagraph (b)(5)

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- Definition

The amount of decrease in the plan assets attributed to the sale, liquidation, spin-off or other divestiture of a corporate division or subsidiary.

+ References

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- Definition

Assets, usually stocks, bonds, and other investments, that have been segregated and restricted (usually in a trust) to provide benefits, at their fair value as of the measurement date. Plan assets include amounts contributed by the employer (and by employees for a contributory plan) and amounts earned from investing the contributions, less benefits paid. If a plan has liabilities other than for benefits, those non-benefit obligations may be considered as reductions of plan assets.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (b)

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-Topic 715

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-Section 35

-Paragraph 50

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- Definition

The amount of increase or decrease in plan assets attributed to foreign currency changes. The effects of foreign currency exchange rate changes that are to be disclosed are those applicable to plans of a foreign operation whose functional currency is not the reporting currency.

+ References

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- Definition

The amount that relates to an irrevocable action that relieves the employer (or the plan) of primary responsibility for a benefit obligation and eliminates significant risks related to the obligation and the assets used to effect the settlement. Examples of transactions that constitute a settlement include (a) making lump-sum cash payments to plan participants in exchange for their rights to receive specified benefits and (b) purchasing nonparticipating annuity contracts.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 30

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-Paragraph 6

-Subparagraph (a)(1)

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