Long-term debt (Details 2) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Long-term Debt
2018		$ 6,194
2019		5,721
2020		4,296
2021		3,128
2022		2,552
Interest paid on short-term and long-term borrowings		1,131	$ 1,075	$ 1,047
Debt Conversion, Original Debt, Amount	$ 381
Debt Conversion, Converted Instrument, Amount	$ 366
Debt Conversion, Converted Instrument, Rate	1.93%
Debt conversion, cash paid	$ 15
Debt exchange premium	$ 33
Medium-term Notes		148
Machinery, Energy & Transportation
Long-term Debt
2018		6
2019		40
2020		6
2021		1,388
2022		$ 504
Financial Products
Long-term Debt
Medium-term notes, weighted-average interest rate (as a percent)		1.80%
Medium-term notes, maximum remaining maturity (in years)		9 years
2018		$ 6,188
2019		5,681
2020		4,290
2021		1,740
2022		$ 2,048