Segment information - Revenue And Operating Profits (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Segment Reporting Information [Line Items]
Revenues	$ 760.3	$ 859.0	$ 1,536.4	$ 1,808.6
Operating Profit (Loss)	(14.6)	8.7	(1.7)	(65.0)
Venezuela impairment	(34.5)		(34.5)	0.0
Share-based compensation adj.	13.1	8.6	24.3	18.7
Total reportable segments
Segment Reporting Information [Line Items]
Revenues	748.1	836.7	1,503.7	1,655.0
Operating Profit (Loss)	52.6	44.9	112.4	93.8
Corporate expenses
Segment Reporting Information [Line Items]
General, administrative and other expenses	(25.3)	(23.3)	(42.9)	(52.9)
Foreign currency transaction gains (loss)	1.1	0.4	(3.7)	(0.3)
Reconciliation of segment policies to GAAP	2.2	2.0	5.4	4.2
Other items not allocated to segments
Segment Reporting Information [Line Items]
Foreign currency transaction gains (loss)	(6.0)	(9.8)	(26.6)	(133.1)
Venezuela impairment	(34.5)		(34.5)
2014 Reorganization and Restructuring	1.2		(0.3)
Mexican settlement losses	(1.1)	(0.9)	(2.4)	(1.7)
U.S. retirement plans	(6.5)	(3.6)	(13.5)	(9.6)
Acquisitions and dispositions	0.3	1.3	0.3	2.5
Share-based compensation adj.		(4.2)		(4.2)
Largest 5 Markets | Total reportable segments
Segment Reporting Information [Line Items]
Revenues	483.9	548.3	971.5	1,083.9
Operating Profit (Loss)	22.1	17.7	50.2	41.3
Global Markets | Total reportable segments
Segment Reporting Information [Line Items]
Revenues	242.1	264.6	487.3	525.1
Operating Profit (Loss)	34.2	28.5	65.4	53.0
Venezuela | Other items not allocated to segments
Segment Reporting Information [Line Items]
Revenues	12.2	22.3	32.7	153.6
Operating Profit (Loss)	1.4	1.9	4.1	36.3
U.S. | Total reportable segments
Segment Reporting Information [Line Items]
Revenues	184.1	180.3	367.7	356.1
Operating Profit (Loss)	6.4	5.9	14.7	7.2
France | Total reportable segments
Segment Reporting Information [Line Items]
Revenues	107.4	133.1	213.1	261.9
Operating Profit (Loss)	6.7	4.9	10.8	11.5
Mexico | Total reportable segments
Segment Reporting Information [Line Items]
Revenues	85.1	98.1	170.8	198.3
Operating Profit (Loss)	4.5	(0.9)	12.4	2.8
Brazil | Total reportable segments
Segment Reporting Information [Line Items]
Revenues	67.7	91.5	141.5	177.9
Operating Profit (Loss)	2.1	5.4	8.2	15.1
Canada | Total reportable segments
Segment Reporting Information [Line Items]
Revenues	39.6	45.3	78.4	89.7
Operating Profit (Loss)	2.4	2.4	4.1	4.7
Latin America | Total reportable segments
Segment Reporting Information [Line Items]
Revenues	91.2	93.1	182.0	183.7
Operating Profit (Loss)	19.2	11.4	35.7	21.5
EMEA | Total reportable segments
Segment Reporting Information [Line Items]
Revenues	112.3	137.5	228.0	274.4
Operating Profit (Loss)	9.1	12.0	17.3	21.2
Asia | Total reportable segments
Segment Reporting Information [Line Items]
Revenues	38.6	34.0	77.3	67.0
Operating Profit (Loss)	5.9	5.1	12.4	10.3
Payment Services | Total reportable segments
Segment Reporting Information [Line Items]
Revenues	22.1	23.8	44.9	46.0
Operating Profit (Loss)	$ (3.7)	$ (1.3)	$ (3.2)	$ (0.5)