Postretirement benefit plans (Details) (USD $) In Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2011		Jun. 30, 2010		Jun. 30, 2011		Jun. 30, 2010
United States Pension Plans of US Entity, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 5		$ 4		$ 11		$ 9
Interest cost	12		12		23		24
Expected return on plan assets	(11)		(12)		(22)		(25)
Amortization of prior service cost	0		0		0		0
Recognized net actuarial loss	6		5		12		10
Net periodic benefit cost	12		9		24		18
Settlement charges	0	[1]	19	[1]	0	[1]	30	[1]
Total, including charges	12		28		24		48
United States Postretirement Benefit Plans of US Entity, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	1		1		2		2
Interest cost	7		6		12		13
Expected return on plan assets	(5)		(6)		(10)		(12)
Amortization of prior service cost	0		1		1		1
Recognized net actuarial loss	3		3		6		6
Net periodic benefit cost	6		5		11		10
Settlement charges	0	[1]	0	[1]	0	[1]	0	[1]
Total, including charges	6		5		11		10
Foreign Pension Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	9		9		18		17
Interest cost	16		15		32		30
Expected return on plan assets	(20)		(18)		(39)		(36)
Amortization of prior service cost	(1)		(1)		(2)		(2)
Recognized net actuarial loss	10		7		19		15
Net periodic benefit cost	14		12		28		24
Settlement charges	0	[1]	0	[1]	0	[1]	0	[1]
Total, including charges	$ 14		$ 12		$ 28		$ 24

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