Segment information - Narrative (Details) $ in Millions	1 Months Ended	3 Months Ended	6 Months Ended	12 Months Ended
	Dec. 31, 2014 Segment employees Region	Jun. 30, 2015 USD ($) Country Region VEF / $	Jun. 30, 2015 Country Segment Region VEF / $	Dec. 31, 2014 USD ($) Region	Feb. 28, 2015 VEF / $	Mar. 31, 2014 VEF / $	Mar. 24, 2014 VEF / $	Mar. 23, 2014 VEF / $
Segment Reporting Information [Line Items]
Number of operating segments | Segment	9		9
Number of countries in which the entity operates, within the five largest markets	5	5	5	5
Number of regions in which the entity operates, within global markets | Region	3	3	3	3
Latin American And EMEA Regions
Restructuring Costs [Abstract]
Positions eliminated across the global workforce | employees	1,700
Severance costs | $				$ 21.8
Charges related to severance and lease terminations | $		$ 0.3
Venezuelan bolívar fuerte
Segment Reporting Information [Line Items]
Remeasurement rate		197	197
Venezuelan bolívar fuerte | Minimum
Segment Reporting Information [Line Items]
Remeasurement rate					52	6.3		6.3
Venezuelan bolívar fuerte | Maximum
Segment Reporting Information [Line Items]
Remeasurement rate					170	50	50