Postretirement benefits Schedule of assumptions used to determine benefit obligation (Details)	Dec. 31, 2017	Dec. 31, 2016
Pension Plan [Member] | UNITED STATES
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract]
Benefit Obligation, Discount Rate	3.59%	4.14%
Benefit Obligation, Rate of Compensation Increase	4.00%	4.00%
Pension Plan [Member] | Non-US [Member]
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract]
Benefit Obligation, Discount Rate	2.76%	2.83%
Benefit Obligation, Rate of Compensation Increase	3.46%	3.57%
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract]
Benefit Obligation, Discount Rate	2.77%	2.97%