Postretirement benefit plans (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013
U.S. Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 5		$ 7
Interest cost	11		11
Expected return on plan assets	(10)		(13)
Amortization of prior service cost (credit)	0		0
Recognized net actuarial loss	6		6
Net periodic benefit costs	12		11
Settlement losses	1	[1]	7	[1]
Total, including other postretirement losses (gains)	13		18
U.S. Retiree Health Care [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	1		1
Interest cost	5		5
Expected return on plan assets	(5)		(6)
Amortization of prior service cost (credit)	1		1
Recognized net actuarial loss	2		3
Net periodic benefit costs	4		4
Settlement losses	0	[1]	0	[1]
Total, including other postretirement losses (gains)	4		4
Non-U.S. Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	10		10
Interest cost	17		16
Expected return on plan assets	(19)		(17)
Amortization of prior service cost (credit)	(1)		(1)
Recognized net actuarial loss	6		10
Net periodic benefit costs	13		18
Settlement losses	0	[1]	0	[1]
Total, including other postretirement losses (gains)	$ 13		$ 18

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