Postretirement benefit plans (Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Defined Benefit Plan Disclosure [Line Items]
Net actuarial gain (loss) from interim remeasurement of defined benefit plans					$ 12		$ 79
Settlement losses					15		22
U.S. Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Net actuarial gain (loss) from interim remeasurement of defined benefit plans					(5)		24
Settlement losses	11	[1]	5	[1]	14	[1]	18	[1]
Curtailment gain	0		0		0		0
Non-U.S. Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Settlement losses	1	[1]	4	[1]	1	[1]	4	[1]
Curtailment gain	2		2		2		5
JAPAN | Non-U.S. Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Net actuarial gain (loss) from interim remeasurement of defined benefit plans					17		55
Curtailment gain					$ 2		$ 5

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