Postretirement benefit plans (Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2014		Jun. 30, 2013		Jun. 30, 2014		Jun. 30, 2013
Defined Benefit Plan Disclosure [Line Items]
Net actuarial gain from interim remeasurement of defined benefit plans			$ 65
U.S. Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Settlement losses	2	[1]	6	[1]	3	[1]	13	[1]
Net actuarial gain from interim remeasurement of defined benefit plans			17
Curtailment gain	0		0		0		0
Non-U.S. Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Settlement losses	0	[1]	0	[1]	0	[1]	0	[1]
Curtailment gain	0		3		0		3
JAPAN | Non-U.S. Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Net actuarial gain from interim remeasurement of defined benefit plans			48
Curtailment gain							$ 3

[1] Includes non-restructuring and restructuring-related settlement losses.