Contractual interest rate for funds borrowed, under the debt agreement.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
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_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Description of the maturity date of the debt instrument including whether the debt matures serially and, if so, a brief description of the serial maturities.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(2))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- Definition

The cash inflow during the period from additional borrowings in aggregate debt. Includes proceeds from short-term and long-term debt.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3255-108585

+ Details

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

- Definition

The cash outflow during the period from the repayment of aggregate short-term and long-term debt. Excludes payment of capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3291-108585

+ Details

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

- Definition

Average Years of Maturity of Long Term Debt

+ References

No definition available.

+ Details

Name:	utx_AverageYearsofMaturityofLongTermDebt
Namespace Prefix:	utx_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Annualized average interest expense rate on short-term and long-term debt

+ References

No definition available.

+ Details

Name:	utx_Averageinterestexpenserate
Namespace Prefix:	utx_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_DebtInstrumentAxis=utx_Notes3.350due2021Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=utx_Notes3.650Due2023Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=utx_Notes3.950Due2025Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=utx_Notes4.125Due2028Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=utx_Notes4.450Due2038Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=utx_Notes4.625Due2048Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=utx_LIBORplus0.650floatingratenotesdue2021Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=utx_Notes1.150Due2024Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=utx_Notes2.150Due2030Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=utx_EURIBORplus0.20floatingratenotesdue2020Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=utx_Juniorsubordinatednotes1.778due2018Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=utx_Notes6800Due2018Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=utx_EURIBORplus0.800floatingratenotesdue2018Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Borrowings and Lines of Credit Borrowings and lines of Credit (Current Year Actions) (Details) € in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018 USD ($)	Sep. 30, 2018 EUR (€)	Sep. 30, 2017
Debt Instrument [Line Items]
Proceeds from Issuance of Debt			$ 11,000
Average Years of Maturity of Long Term Debt			11 years	11 years
Average interest expense rate	3.60%	3.60%	3.50%	3.50%	3.60%
Notes 3.350% Due 2021 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.35%		3.35%	3.35%
Debt Instrument, Maturity Date, Description			2021	2021
Proceeds from Issuance of Debt			$ 1,000
Notes 3.650% Due 2023 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.65%		3.65%	3.65%
Debt Instrument, Maturity Date, Description			2023	2023
Proceeds from Issuance of Debt			$ 2,000
Notes 3.950% Due 2025 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	3.95%		3.95%	3.95%
Debt Instrument, Maturity Date, Description			2025	2025
Proceeds from Issuance of Debt			$ 2,000
Notes 4.125% Due 2028 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.125%		4.125%	4.125%
Debt Instrument, Maturity Date, Description			2028	2028
Proceeds from Issuance of Debt			$ 3,000
Notes 4.450% Due 2038 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.45%		4.45%	4.45%
Debt Instrument, Maturity Date, Description			2038	2038
Proceeds from Issuance of Debt			$ 750
Notes 4.625% Due 2048 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.625%		4.625%	4.625%
Debt Instrument, Maturity Date, Description			2048	2048
Proceeds from Issuance of Debt			$ 2,000
LIBOR plus 0.650% floating rate notes due 2021 [Member]
Debt Instrument [Line Items]
Debt Instrument, Maturity Date, Description			2021	2021
Proceeds from Issuance of Debt			$ 750
Notes 1.150% Due 2024 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	1.15%		1.15%	1.15%
Debt Instrument, Maturity Date, Description			2024	2024
Proceeds from Issuance of Debt \| €				€ 750
Notes 2.150% Due 2030 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	2.15%		2.15%	2.15%
Debt Instrument, Maturity Date, Description			2030	2030
Proceeds from Issuance of Debt \| €				€ 500
EURIBOR plus 0.20% floating rate notes due 2020 [Member]
Debt Instrument [Line Items]
Debt Instrument, Maturity Date, Description			2020	2020
Proceeds from Issuance of Debt \| €				€ 750
Junior subordinated notes 1.778% due 2018 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	1.778%		1.778%	1.778%
Debt Instrument, Maturity Date, Description			2018	2018
Repayments of Debt			$ 1,000
Notes 6.800% Due 2018 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	6.80%		6.80%	6.80%
Debt Instrument, Maturity Date, Description			2018	2018
Repayments of Debt			$ 99
EURIBOR plus 0.800% floating rate notes due 2018 [Member]
Debt Instrument [Line Items]
Debt Instrument, Maturity Date, Description			2018	2018
Repayments of Debt \| €				€ 750