Acquisitions, Dispositions, Goodwill and Other Intangible Assets (Variable Interest Entity) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Current Assets	$ 1,636
Variable Interest Entity, Consolidated, Carrying Amount, Current Liabilities	1,821
Variable Interest Entity, Consolidated, Carrying Amount, Noncurrent Assets	1,023
Variable Interest Entity, Consolidated, Carrying Amount, Assets	2,659
Variable Interest Entity, Consolidated, Carrying Amount, Noncurrent Liabilities	1,067
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities	$ 2,888

The carrying amount of the consolidated Variable Interest Entity's assets included in the reporting entity's statement of financial position.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 810

-SubTopic 10

-Section 50

-Paragraph 3

-Subparagraph (bb)

-URI http://asc.fasb.org/extlink&oid=28200181&loc=d3e5710-111685

+ Details

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Balance Type:	debit
Period Type:	instant

- Definition

The carrying amount of the consolidated Variable Interest Entity's liabilities included in the reporting entity's statement of financial position.

+ References

+ Details

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Namespace Prefix:	us-gaap_
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- Details

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The carrying amount of the consolidated Variable Interest Entity's current assets included in the reporting entity's statement of financial position.

+ References

No definition available.

+ Details

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Namespace Prefix:	utx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The carrying amount of the consolidated Variable Interest Entity's current liabilities included in the reporting entity's statement of financial position.

+ References

No definition available.

+ Details

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Namespace Prefix:	utx_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The carrying amount of the consolidated Variable Interest Entity's noncurrent assets included in the reporting entity's statement of financial position.

+ References

No definition available.

+ Details

Name:	utx_VariableInterestEntityConsolidatedCarryingAmountNoncurrentAssets
Namespace Prefix:	utx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The carrying amount of the consolidated Variable Interest Entity's noncurrent liabilities included in the reporting entity's statement of financial position.

+ References

No definition available.

+ Details

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Namespace Prefix:	utx_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant