Goodwill and Intangible Assets (Goodwill balance by business segment) (Details)	3 Months Ended	6 Months Ended		9 Months Ended
	Mar. 31, 2019 USD ($) segment	Sep. 30, 2019 USD ($) segment	Jun. 30, 2019 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)
Goodwill Information
Number of business combinations completed					0
Purchased goodwill from acquisitions		$ 508,000,000		$ 508,000,000
Goodwill
Balance at the beginning of the period	$ 10,051,000,000		$ 10,051,000,000	10,051,000,000
Acquisition activity				508,000,000
Divestiture activity				(49,000,000)
Translation and other				(100,000,000)
Balance at the end of the period		$ 10,410,000,000		10,410,000,000
Number of business segments | segment	5	4
Previous Number Of Reportable Segments | segment		4
Amount of Goodwill impairment			0
Safety and Industrial
Goodwill
Balance at the beginning of the period	$ 4,716,000,000		4,716,000,000	4,716,000,000
Divestiture activity				(49,000,000)
Translation and other				(51,000,000)
Balance at the end of the period		$ 4,616,000,000		4,616,000,000
Transportation and Electronics
Goodwill
Balance at the beginning of the period	1,857,000,000		1,857,000,000	1,857,000,000
Translation and other				(27,000,000)
Balance at the end of the period		1,830,000,000		1,830,000,000
Health Care
Goodwill
Balance at the beginning of the period	3,248,000,000		3,248,000,000	3,248,000,000
Acquisition activity				508,000,000
Translation and other				(53,000,000)
Balance at the end of the period		3,703,000,000		3,703,000,000
Consumer
Goodwill
Balance at the beginning of the period	$ 230,000,000		$ 230,000,000	230,000,000
Translation and other				31,000,000
Balance at the end of the period		$ 261,000,000		$ 261,000,000