Guarantees (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014
Guarantee Obligations [Line Items]
Environmental, health and safety, tax employment matters	$ 171	$ 186
Balance as of January 1	1,264	1,324
Warranties and performance guarantees issued	291	302
Settlements made	259	322
Other	(84)	(40)
Balance as of December 31	1,212	1,264
Credit Facilities And Debt Obligations Unconsolidated Subsidiaries (expire 2015 to 2034)
Guarantee Obligations [Line Items]
Maximum Potential Payment	241	211
Carrying Amount of Liability	0	15
Commercial aerospace financing arrangements (see Note 5)
Guarantee Obligations [Line Items]
Maximum Potential Payment	365	411
Carrying Amount of Liability	12	18
Performance Guarantee
Guarantee Obligations [Line Items]
Maximum Potential Payment	55	136
Carrying Amount of Liability	$ 3	$ 0

The current carrying amount of the liability for the freestanding or embedded guarantor's obligations under the guarantee or each group of similar guarantees.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6851643&loc=d3e12069-110248

+ Details

Name:	us-gaap_GuaranteeObligationsCurrentCarryingValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

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.

+ References

No definition available.

+ Details

Name:	us-gaap_GuaranteeObligationsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum potential amount of future payments (undiscounted) the guarantor could be required to make under the guarantee or each group of similar guarantees before reduction for potential recoveries under recourse or collateralization provisions.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=6851643&loc=d3e12069-110248

+ Details

Name:	us-gaap_GuaranteeObligationsMaximumExposure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Carrying value as of the balance sheet date of obligations incurred through that date and payable for estimated claims under standard and extended warranty protection rights granted to customers.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 8
-Subparagraph ((c)(5))
-URI http://asc.fasb.org/extlink&oid=51674963&loc=d3e12565-110249

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.15(5))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

Name:	us-gaap_ProductWarrantyAccrual
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Represents the aggregate decrease in the liability related to payments to satisfy claims for standard and extended product warranties.

+ References

+ Details

Name:	us-gaap_ProductWarrantyAccrualPayments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Represents the aggregate increase in the liability for accruals related to standard and extended product warranties issued during the reporting period.

+ References

+ Details

Name:	us-gaap_ProductWarrantyAccrualWarrantiesIssued
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The current carrying amount of the liability for the freestanding or embedded guarantor's obligations under the guarantee or each group of similar guarantees. The element is for the carrying amount of guarantees not otherwise reported.

+ References

No definition available.

+ Details

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

- Definition

Represents the aggregate increase (decrease) in the liability related to other items, including currency translation.

+ References

No definition available.

+ Details

Name:	utx_ProductWarrantyAccrualOther
Namespace Prefix:	utx_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	us-gaap_GuaranteeObligationsByNatureAxis=utx_CreditFacilitiesAndDebtObligationsUnconsolidatedSubsidiariesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_GuaranteeObligationsByNatureAxis=utx_CommercialAerospaceMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_GuaranteeObligationsByNatureAxis=us-gaap_PerformanceGuaranteeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: