Segment information - Revenue And Operating Profits (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting Information [Line Items]
Revenues	$ 803.5	$ 755.8	$ 739.5	$ 721.8	$ 765.8	$ 759.2	$ 760.3	$ 776.1	$ 3,020.6	$ 3,061.4	$ 3,562.3
Operating Profit (Loss)	$ 58.3	$ 50.0	$ 22.1	$ 13.8	$ 33.0	$ 25.3	$ (14.6)	12.9	144.2	56.6	(27.5)
Foreign currency transaction losses								$ (18.0)	1.4	(26.8)	(127.2)
Share-based compensation adj.									10.7	0.8	(136.9)
Reportable Segments:
Segment Reporting Information [Line Items]
Revenues									2,908.4	2,976.9	3,350.5
Operating Profit (Loss)									264.7	242.0	239.9
Corporate items:
Segment Reporting Information [Line Items]
General, administrative and other expenses									(59.8)	(81.0)	(110.8)
Foreign currency transaction losses									3.8	(8.8)	(2.6)
Reconciliation of segment policies to GAAP									(2.2)	4.6	(2.3)
Other items not allocated to segments:
Segment Reporting Information [Line Items]
Acquisitions and dispositions, Revenues									2.8
Reorganization and Restructuring									(30.3)	(15.3)	(21.8)
U.S. and Mexican retirement plans									(31.5)	(31.2)	(79.0)
Acquisitions and dispositions, Operating Profit (Loss)									(16.3)	(6.0)	49.4
Share-based compensation adj.											(2.4)
Largest 5 Markets | Reportable Segments:
Segment Reporting Information [Line Items]
Revenues									1,908.3	1,919.0	2,177.2
Operating Profit (Loss)									101.9	108.5	118.8
Global Markets | Reportable Segments:
Segment Reporting Information [Line Items]
Revenues									910.0	972.0	1,076.7
Operating Profit (Loss)									160.5	140.7	126.0
Venezuela
Segment Reporting Information [Line Items]
Foreign currency transaction losses									(4.8)
Venezuela | Other items not allocated to segments:
Segment Reporting Information [Line Items]
Revenues									109.4	84.5	211.8
Operating Profit (Loss)									15.8	(47.7)	(97.9)
U.S. | Reportable Segments:
Segment Reporting Information [Line Items]
Revenues									752.6	730.4	727.8
Operating Profit (Loss)									6.3	15.1	22.8
France | Reportable Segments:
Segment Reporting Information [Line Items]
Revenues									424.5	431.5	517.4
Operating Profit (Loss)									36.8	34.7	39.4
Mexico | Reportable Segments:
Segment Reporting Information [Line Items]
Revenues									295.3	333.0	388.2
Operating Profit (Loss)									20.4	24.2	9.6
Brazil | Reportable Segments:
Segment Reporting Information [Line Items]
Revenues									285.7	270.4	364.1
Operating Profit (Loss)									30.1	23.8	34.2
Canada | Reportable Segments:
Segment Reporting Information [Line Items]
Revenues									150.2	153.7	179.7
Operating Profit (Loss)									8.3	10.7	12.8
Latin America | Reportable Segments:
Segment Reporting Information [Line Items]
Revenues									355.1	369.9	380.6
Operating Profit (Loss)									89.9	76.3	50.4
EMEA | Reportable Segments:
Segment Reporting Information [Line Items]
Revenues									387.4	444.7	556.3
Operating Profit (Loss)									40.1	35.7	52.5
Asia | Reportable Segments:
Segment Reporting Information [Line Items]
Revenues									167.5	157.4	139.8
Operating Profit (Loss)									30.5	28.7	23.1
Payment Services | Reportable Segments:
Segment Reporting Information [Line Items]
Revenues									90.1	85.9	96.6
Operating Profit (Loss)									$ 2.3	$ (7.2)	$ (4.9)