Segment information Segment informations - Assets by Segment (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Assets held by Segment	$ 2,162.9	$ 1,994.8
Reportable segments
Segment Reporting Information [Line Items]
Assets held by Segment	1,763.7	1,622.6
Reportable segments | North America
Segment Reporting Information [Line Items]
Assets held by Segment	705.4	629.4
Reportable segments | South America
Segment Reporting Information [Line Items]
Assets held by Segment	398.2	371.4
Reportable segments | Rest of World
Segment Reporting Information [Line Items]
Assets held by Segment	660.1	621.8
Corporate items
Segment Reporting Information [Line Items]
Assets held by Segment	325.0	321.3
Venezuela | Other items not allocated to segments
Segment Reporting Information [Line Items]
Assets held by Segment	$ 74.2	$ 50.9