Postretirement benefit plans (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended	6 Months Ended
	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2013 U.S. Defined Benefit [Member]	Jun. 30, 2012 U.S. Defined Benefit [Member]	Jun. 30, 2013 U.S. Defined Benefit [Member]	Jun. 30, 2012 U.S. Defined Benefit [Member]	Jun. 30, 2013 U.S. Retiree Health Care [Member]	Jun. 30, 2012 U.S. Retiree Health Care [Member]	Jun. 30, 2013 U.S. Retiree Health Care [Member]	Jun. 30, 2012 U.S. Retiree Health Care [Member]	Jun. 30, 2013 Non-U.S. Defined Benefit [Member]	Jun. 30, 2012 Non-U.S. Defined Benefit [Member]	Jun. 30, 2013 Non-U.S. Defined Benefit [Member]	Jun. 30, 2012 Non-U.S. Defined Benefit [Member]	Jun. 30, 2013 JAPAN Non-U.S. Defined Benefit [Member]	Jun. 30, 2013 JAPAN Non-U.S. Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost			$ 7	$ 6	$ 14	$ 12	$ 2	$ 1	$ 3	$ 2	$ 10	$ 10	$ 20	$ 20
Interest cost			10	11	21	23	5	6	10	12	15	20	31	39
Expected return on plan assets			(12)	(12)	(25)	(25)	(6)	(6)	(12)	(11)	(16)	(20)	(33)	(40)
Amortization of prior service cost (credit)			0	0	0	0	1	1	2	2	(1)	(1)	(2)	(2)
Recognized net actuarial loss			5	4	11	8	3	3	6	6	7	11	17	23
Net periodic benefit cost			10	9	21	18	5	5	9	11	15	20	33	40
Settlement loss			6	0	13	0	0	0	0	0	0	0	0	0
Curtailment gain			0	0	0	0	0	0	0	(1)	(3)	0	(3)	0		(3)
Special termination benefit gain					0	(2)			0	0			0	0
Total, including other postretirement (gains) losses			16	9	34	16	5	5	9	10	12	20	30	40
Net actuarial gain from interim remeasurement of defined benefit plan	65		17												48
Overfunded retirement plans	106	68
Underfunded retirement plans	$ 240	$ 269