Property, Plant and Equipment - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Property, Plant and Equipment [Line Items]
Net Cost of Assets under capital leases	$ 1stm_NetCostOfAssetsUnderCapitalLeases	$ 1stm_NetCostOfAssetsUnderCapitalLeases
Depreciation charge	750us-gaap_Depreciation	838us-gaap_Depreciation	930us-gaap_Depreciation
Capital investment funding		3stm_CapitalInvestmentFunding	1stm_CapitalInvestmentFunding
Reduction in depreciation charges due to public funding	4	6	10
Cash proceeds from sale of equipment	9	12	16
Assets held for sale	31
Maximum [Member]
Property, Plant and Equipment [Line Items]
Capital investment funding	$ 1

Capital investment funding.

No definition available.

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- Definition

Net Cost Of Assets Under Capital Leases

+ References

No definition available.

+ Details

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Namespace Prefix:	stm_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Reduction in depreciation charges due to Public funding.

+ References

No definition available.

+ Details

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Namespace Prefix:	stm_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount classified as assets attributable to disposal group held for sale or disposed of.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 205

-SubTopic 20

-Section 45

-Paragraph 10

-URI http://asc.fasb.org/extlink&oid=6892542&loc=d3e1107-107759

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount of expense recognized in the current period that reflects the allocation of the cost of tangible assets over the assets' useful lives. Includes production and non-production related depreciation.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585

+ Details

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Balance Type:	debit
Period Type:	duration

- Definition

The cash inflow from sale of machinery and equipment.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Investing Activities

-URI http://asc.fasb.org/extlink&oid=6516133

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 12

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3179-108585

+ Details

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- Details

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