Income Taxes (Unrecognized Tax Benefits) (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Apr. 30, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Uncertainties [Abstract]
Balance at January 1		$ 1,347	$ 1,619	$ 1,189
Additions for tax positions related to the current year		125	131	192
Additions for tax positions of prior years		323	73	344
Reductions for tax positions of prior years		(83)	(101)	(91)
Settlements		(48)	(375)	(15)
Separation of Carrier and Otis	$ 439	(439)
Balance at December 31		1,225	1,347	1,619
Gross interest expense related to unrecognized tax benefits		50	57	37
Total accrued interest balance at December 31	$ 165	$ 141	$ 249	$ 255