Business Combinations (Rockwell Collins Proforma Information) (Details) - Rockwell Collins [Member] $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($) $ / shares
Business Acquisition [Line Items]
Business Acquisition, Pro Forma Revenue	$ 42,336
Business Acquisition, Pro Forma Net Income (Loss)	$ 2,011
Business Acquisition, Pro Forma Income (Loss) from Continuing Operations, Net of Tax, Per Share, Basic | $ / shares	$ 2.26
Business Acquisition, Pro Forma Income (Loss) from Continuing Operations, Net of Tax, Per Share, Diluted | $ / shares	$ 2.24
Pro Forma Nonrecurring Adjustment, Amortization of inventory and fixed asset fair value adjustment	$ 58
Pro Forma Nonrecurring Adjustment, Amortization of acquired Rockwell Collins intangible assets, net	(193)
Pro Forma Nonrecurring Adjustment, Utilization of contractual customer obligation	16
Pro Forma Nonrecurring Adjustment, UTC/Rockwell fees for advisory, legal, accounting services	212
Pro Forma Nonrecurring Adjustment, Interest expense incurred on acquisition financing, net	(199)
Pro Forma Nonrecurring Adjustment, Elimination of capitalized pre-production engineering amortization	63
Pro Forma Nonrecurring Adjustment, Adjustment to net periodic pension cost	42
Pro Forma Nonrecurring Adjustment, Adjustment to reflect the adoption of ASC 606	106
Pro Forma Nonrecurring Adjustment, Elimination of entities held for sale	(47)
Pro Forma Nonrecurring Adjustments, Net	$ 58