Guarantees (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Product Warranty Liability [Line Items]
Balance as of January 1	$ 1,146	$ 1,199
Warranties and performance guarantees issued	115	78
Settlements made	106	56
Other	6	1
Balance as of September 30	$ 1,161	$ 1,222