Segment information - Revenue And Operating Profits (Details) - USD ($) $ in Millions	3 Months Ended				9 Months Ended
	Sep. 30, 2015	Jun. 30, 2015	Sep. 30, 2014	Jun. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Segment Reporting Information [Line Items]
Revenues	$ 759.2		$ 872.5		$ 2,295.6	$ 2,681.1
Operating Profit (Loss)	25.3		61.2		23.6	(3.8)
Venezuela impairment	(0.8)	$ (34.5)			(35.3)	0.0
Share-based compensation adj.	13.5		8.9		37.8	27.6
Total reportable segments
Segment Reporting Information [Line Items]
Revenues	739.9		847.4		2,243.6	2,502.4
Operating Profit (Loss)	57.9		59.0		170.3	152.8
Corporate expenses
Segment Reporting Information [Line Items]
General, administrative and other expenses	(15.5)		(37.4)		(58.4)	(90.3)
Foreign currency transaction losses	(5.1)		(0.5)		(8.8)	(0.8)
Reconciliation of segment policies to GAAP	(0.3)		(0.3)		5.1	3.9
Other items not allocated to segments
Segment Reporting Information [Line Items]
Foreign currency transaction losses	(3.8)		(4.8)		(30.4)	(137.9)
Venezuela impairment	(0.8)				(35.3)
Mexican settlement losses	(1.5)		(2.3)		(3.9)	(4.0)
U.S. retirement plans	(6.5)		(3.7)		(20.0)	(13.3)
Acquisitions and dispositions	0.0		46.9		0.3	49.4
Share-based compensation adj.			1.8	$ (4.2)		(2.4)
Largest 5 Markets | Total reportable segments
Segment Reporting Information [Line Items]
Revenues	475.3		551.2		1,446.8	1,635.1
Operating Profit (Loss)	25.8		29.0		76.0	70.3
Global Markets | Total reportable segments
Segment Reporting Information [Line Items]
Revenues	242.9		270.8		730.2	795.9
Operating Profit (Loss)	34.1		32.4		99.5	85.4
Venezuela | Other items not allocated to segments
Segment Reporting Information [Line Items]
Revenues	19.3		25.1		52.0	178.7
Operating Profit (Loss)	3.8		2.5		7.9	38.8
U.S. | Total reportable segments
Segment Reporting Information [Line Items]
Revenues	182.6		181.6		550.3	537.7
Operating Profit (Loss)	1.4		3.9		16.1	11.1
France | Total reportable segments
Segment Reporting Information [Line Items]
Revenues	110.8		132.7		323.9	394.6
Operating Profit (Loss)	13.7		16.7		24.5	28.2
Mexico | Total reportable segments
Segment Reporting Information [Line Items]
Revenues	80.4		95.1		251.2	293.4
Operating Profit (Loss)	3.4		(0.4)		15.8	2.4
Brazil | Total reportable segments
Segment Reporting Information [Line Items]
Revenues	63.6		95.8		205.1	273.7
Operating Profit (Loss)	3.7		4.8		11.9	19.9
Canada | Total reportable segments
Segment Reporting Information [Line Items]
Revenues	37.9		46.0		116.3	135.7
Operating Profit (Loss)	3.6		4.0		7.7	8.7
Latin America | Total reportable segments
Segment Reporting Information [Line Items]
Revenues	91.7		95.4		273.7	279.1
Operating Profit (Loss)	17.6		10.7		53.3	32.2
EMEA | Total reportable segments
Segment Reporting Information [Line Items]
Revenues	111.5		139.1		339.5	413.5
Operating Profit (Loss)	9.4		15.5		26.7	36.7
Asia | Total reportable segments
Segment Reporting Information [Line Items]
Revenues	39.7		36.3		117.0	103.3
Operating Profit (Loss)	7.1		6.2		19.5	16.5
Payment Services | Total reportable segments
Segment Reporting Information [Line Items]
Revenues	21.7		25.4		66.6	71.4
Operating Profit (Loss)	(2.0)		$ (2.4)		(5.2)	$ (2.9)
2014 Reorganization and Restructuring | Other items not allocated to segments
Segment Reporting Information [Line Items]
Reorganization and Restructuring	(0.9)				(1.2)
2015 Reorganization and Restructuring
Segment Reporting Information [Line Items]
Reorganization and Restructuring	(2.0)
2015 Reorganization and Restructuring | Other items not allocated to segments
Segment Reporting Information [Line Items]
Reorganization and Restructuring	$ (2.0)				$ (2.0)