Employee Benefit Plans Employee Benefit Plans (Disc Ops) (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Defined Pension, Defined Contribution and Other Postretirement Benefits [Abstract]
Disposal Group, Including Discontinued Operation, Recognized Net (Gain) Loss Due to Curtailments	$ 110	$ 0	$ 110	$ 0
Defined Benefit Plan, Net Periodic Benefit Cost, Discontinued Operations	$ 25	$ 24	$ 74	$ 72

Amount of net (gain) loss recognized in net periodic benefit cost due to pension curtailments related to discontinued operations. Curtailments result from an event that significantly reduces the expected years of future service of present employees or eliminates for a significant number of employees the accrual of defined benefits for some or all of their future services.

No definition available.

Name:	utx_DisposalGroupIncludingDiscontinuedOperationRecognizedNetGainLossDuetoCurtailments
Namespace Prefix:	utx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration