Accumulated other comprehensive income (loss) (Details 2) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Other income (expense)									$ 207		$ 146		$ 161
Interest expense excluding Financial Products									(531)		(505)		(507)
Interest expense of Financial Products									(646)		(596)		(587)
Consolidated profit before taxes									4,082		139		3,439
Tax (provision) benefit									(3,339)		(192)		(916)
Reclassifications net of tax	$ (1,299)	$ 1,059	$ 802	$ 192	$ (1,171)	$ 283	$ 550	$ 271	754	[1]	(67)	[1]	2,512	[1]
Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Reclassifications net of tax									(9)		52		(17)
Reclassification out of Accumulated Other Comprehensive Income | Foreign currency translation
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Other income (expense)									(13)		(17)		0
Tax (provision) benefit									0		0		0
Reclassifications net of tax									(13)		(17)		0
Reclassification out of Accumulated Other Comprehensive Income | Pension and other postretirement benefits
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Amortization of prior service credit (cost)									25		56		53
Tax (provision) benefit									(9)		(21)		(18)
Reclassifications net of tax									16		35		35
Reclassification out of Accumulated Other Comprehensive Income | Derivative financial instruments
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Consolidated profit before taxes									(121)		5		(139)
Tax (provision) benefit									44		(2)		51
Reclassifications net of tax									(77)		3		(88)
Reclassification out of Accumulated Other Comprehensive Income | Derivative financial instruments | Foreign exchange contracts | Machinery, Energy & Transportation
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Other income (expense)									(121)		14		(127)
Reclassification out of Accumulated Other Comprehensive Income | Derivative financial instruments | Foreign exchange contracts | Financial Products
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Interest expense of Financial Products									(6)		0		0
Reclassification out of Accumulated Other Comprehensive Income | Derivative financial instruments | Interest rate contracts | Machinery, Energy & Transportation
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Interest expense excluding Financial Products									(9)		(6)		(6)
Reclassification out of Accumulated Other Comprehensive Income | Derivative financial instruments | Interest rate contracts | Financial Products
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Interest expense of Financial Products									3		(3)		(6)
Reclassification out of Accumulated Other Comprehensive Income | Available-for-sale securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income
Other income (expense)									100		46		56
Tax (provision) benefit									(35)		(15)		(20)
Reclassifications net of tax									$ 65		$ 31		$ 36

[1] 1 Profit (loss) attributable to common shareholders.