Postretirement benefit plans (Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net actuarial gain from interim remeasurement of defined benefit plan	$ 14		$ 79
Gain on transfer of Japan substitutional pension	0	144	0	144
U.S. Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net actuarial gain from interim remeasurement of defined benefit plan	7		24
Special termination benefit gain	0	0	0	2
Settlement loss	5	0	18	0
Non-U.S. Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Special termination benefit gain	0	337	0	337
Settlement loss	4	193	4	193
Non-U.S. Defined Benefit [Member] | Difference Between Fair Values of the Obligations Settled and Assets Transferred [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Special termination benefit gain		337
Non-U.S. Defined Benefit [Member] | Obligation and Assets Transferred to Japan Subsitutional Pension [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined Benefit Plan, Benefit Obligation		533		533
Defined Benefit Plan, Fair Value of Plan Assets		196		196
Non-U.S. Defined Benefit [Member] | Offset By Settlement Loss Related to Recognition of Previously Unrecognized Actuarial Losses Included In AOCI [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Settlement loss		193
Non-U.S. Defined Benefit [Member] | JAPAN
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net actuarial gain from interim remeasurement of defined benefit plan	$ 7		$ 55