Postretirement benefits Components of net periodic benefit costs (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	$ 20	$ 22
Interest Cost	33	35
Expected Return on Plan Assets	(57)	(47)
Amortization of Actuarial (Gain) Loss		1
Amortization of Prior Service Cost	0
Net Periodic Benefit Cost	(4)	11
Pension Plan [Member] | UNITED STATES
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	16	17
Interest Cost	26	27
Expected Return on Plan Assets	(47)	(37)
Amortization of Actuarial (Gain) Loss		0
Amortization of Prior Service Cost	0
Net Periodic Benefit Cost	(5)	7
Pension Plan [Member] | Non-US [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	4	5
Interest Cost	7	8
Expected Return on Plan Assets	(10)	(10)
Amortization of Actuarial (Gain) Loss		1
Amortization of Prior Service Cost	0
Net Periodic Benefit Cost	1	4
Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	0	2
Interest Cost	1	5
Expected Return on Plan Assets	(1)	(2)
Amortization of Actuarial (Gain) Loss		0
Amortization of Prior Service Cost	(23)
Net Periodic Benefit Cost	(23)	5
Other Postretirement Benefit Plan [Member] | UNITED STATES
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	0	2
Interest Cost	1	5
Expected Return on Plan Assets	(1)	(2)
Amortization of Actuarial (Gain) Loss		0
Amortization of Prior Service Cost	(23)
Net Periodic Benefit Cost	(23)	5
Other Postretirement Benefit Plan [Member] | Non-US [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service Cost	0	0
Interest Cost	0	0
Expected Return on Plan Assets	0	0
Amortization of Actuarial (Gain) Loss		0
Amortization of Prior Service Cost	0
Net Periodic Benefit Cost	$ 0	$ 0