Accumulated Other Comprehensive Loss (Summary of Changes in AOCI) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020	Dec. 31, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax	$ (3,939)	$ (8,012)	$ (3,939)	$ (8,012)	$ (3,555)	$ (3,734)	$ (8,800)	$ (10,149)
Other comprehensive (loss) income before reclassifications, net - Foreign Currency Translation	(321)	605	(239)	(175)
Other Comprehensive (Income) Loss, Defined Benefit Plan, before Reclassification Adjustment and Tax	22	(12)	(2)	(2,375)
Other comprehensive (loss) income before reclassifications, net - Unrealized Hedging Gains (Losses)	(175)	117	(113)	(98)
Other comprehensive (loss) income before reclassifications, net	(474)	710	(354)	(2,648)
Amounts reclassified, pretax - Foreign Currency Translation	0	0	0	0
Amounts reclassified, pretax - Pension	64	95	192	282
Amounts reclassified, pretax - Unrealized Hedging Gains (Losses)	8	37	(26)	93
Amounts reclassified, pre-tax	72	132	166	375
Tax benefit (expense) - Foreign Currency Translation	(5)	7	(8)	19
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, Tax	(16)	(22)	(39)	515
Tax benefit (expense) - Unrealized Hedging Gains (Losses)	39	(39)	30	1
Income tax (expense) benefit related to items of other comprehensive income (loss)	18	(54)	(17)	535
Other Comprehensive Income (Loss), Foreign Currency Transaction, Effect of Separation of Otis and Carrier				3,287
Other Comprehensive Income (Loss), Defined Benefit Plan, Effect of Separation of Otis and Carrier				584
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives, Effect of Separation of Otis and Carrier				4
Other Comprehensive Income (Loss), Effect of Separation of Otis and Carrier				3,875
Foreign Currency Translation
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax	463	(80)	463	(80)	789	710	(692)	(3,211)
Defined Benefit Pension and Post-retirement Plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax	(4,332)	(7,766)	(4,332)	(7,766)	(4,402)	(4,483)	(7,827)	(6,772)
Unrealized hedging (losses) gains
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax	$ (70)	$ (166)	$ (70)	$ (166)	$ 58	$ 39	$ (281)	$ (166)