Pension plans (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Compensation and Retirement Disclosure [Abstract]
Expenses recognized during period under the defined contributions plans	$ 111	$ 99	$ 96
Fair value of plan assets	566	487
Projected benefit obligation	591	531
Accrued pension liability	25	44
Defined pension plan contribution expected for 2014	3
Estimated net actuarial loss expected to be amortized from AOCI	3
Benefit payments made during period	26	37
Benefit payments for settlement of a defined benefit plan		$ 12