Postretirement benefit plans (Details) (USD $) In Millions	3 Months Ended				9 Months Ended
	Sep. 30, 2011		Sep. 30, 2010		Sep. 30, 2011		Sep. 30, 2010
United States Pension Plans of US Entity, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 6		$ 5		$ 17		$ 15
Interest cost	11		11		34		35
Expected return on plan assets	(11)		(12)		(34)		(37)
Amortization of prior service cost	0		0		1		1
Recognized net actuarial loss	6		7		17		16
Net periodic benefit cost	12		11		35		30
Settlement charges	0	[1]	5	[1]	0	[1]	34	[1]
Total, including charges	12		16		35		64
United States Postretirement Benefit Plans of US Entity, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	1		1		3		3
Interest cost	6		6		19		19
Expected return on plan assets	(5)		(6)		(16)		(17)
Amortization of prior service cost	1		1		2		2
Recognized net actuarial loss	3		3		9		9
Net periodic benefit cost	6		5		17		16
Settlement charges	0	[1]	0	[1]	0	[1]	0	[1]
Total, including charges	6		5		17		16
Foreign Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	9		8		27		25
Interest cost	16		16		48		46
Expected return on plan assets	(20)		(19)		(59)		(54)
Amortization of prior service cost	(1)		(1)		(3)		(3)
Recognized net actuarial loss	10		8		29		22
Net periodic benefit cost	14		12		42		36
Settlement charges	0	[1]	0	[1]	0	[1]	0	[1]
Total, including charges	$ 14		$ 12		$ 42		$ 36

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