Segment information - Capital Expenditures, Depreciation, Amortization (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Segment Reporting Information [Line Items]
Capital expenditures by business segments	$ 53.7	$ 26.3	$ 32.3	$ 23.8	$ 53.7	$ 43.1	$ 43.6	$ 32.5	$ 136.1	$ 172.9	$ 170.9
Depreciation and amortization by business segments	39.4	39.7	40.9	41.9	44.8	40.4	40.4	40.2	161.9	165.8	148.4
Property and Equipment [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization by business segments									156.4	159.4	141.2
Largest 5 Markets [Member]
Segment Reporting Information [Line Items]
Capital expenditures by business segments									83.4	103.5	103.7
Largest 5 Markets [Member] | Property and Equipment [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization by business segments									106.0	107.7	98.2
Largest 5 Markets [Member] | Intangible assets member [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization by business segments									1.7	2.3	2.7
Global Markets [Member]
Segment Reporting Information [Line Items]
Capital expenditures by business segments									35.2	38.1	51.5
Global Markets [Member] | Property and Equipment [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization by business segments									38.7	43.1	37.2
Global Markets [Member] | Intangible assets member [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization by business segments									2.3	2.6	3.8
Payment Services [Member]
Segment Reporting Information [Line Items]
Capital expenditures by business segments									0.8	1.5	1.8
Payment Services [Member] | Property and Equipment [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization by business segments									2.2	2.2	1.3
Payment Services [Member] | Intangible assets member [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization by business segments									1.5	1.5	0.7
Business Segments [Member]
Segment Reporting Information [Line Items]
Capital expenditures by business segments									119.4	143.1	157.0
Business Segments [Member] | Property and Equipment [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization by business segments									146.9	153.0	136.7
Business Segments [Member] | Intangible assets member [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization by business segments									5.5	6.4	7.2
Corporate Items [Member]
Segment Reporting Information [Line Items]
Capital expenditures by business segments									16.7	29.8	13.9
Corporate Items [Member] | Property and Equipment [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization by business segments									9.5	6.4	4.5
Corporate Items [Member] | Intangible assets member [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization by business segments									0	0	0
Latin America [Member] | Global Markets [Member]
Segment Reporting Information [Line Items]
Capital expenditures by business segments									22.4	26.8	37.3
Latin America [Member] | Global Markets [Member] | Property and Equipment [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization by business segments									21.9	22.5	21.1
Latin America [Member] | Global Markets [Member] | Intangible assets member [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization by business segments									0.3	0.4	0.4
Europe, Middle East and Africa [Member] | Global Markets [Member]
Segment Reporting Information [Line Items]
Capital expenditures by business segments									9.2	8.9	9.8
Europe, Middle East and Africa [Member] | Global Markets [Member] | Property and Equipment [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization by business segments									13.6	16.9	12.5
Europe, Middle East and Africa [Member] | Global Markets [Member] | Intangible assets member [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization by business segments									1.1	1.2	2.3
Asia Pacific [Member] | Global Markets [Member]
Segment Reporting Information [Line Items]
Capital expenditures by business segments									3.6	2.4	4.4
Asia Pacific [Member] | Global Markets [Member] | Property and Equipment [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization by business segments									3.2	3.7	3.6
Asia Pacific [Member] | Global Markets [Member] | Intangible assets member [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization by business segments									0.9	1.0	1.1
US [Member] | Largest 5 Markets [Member]
Segment Reporting Information [Line Items]
Capital expenditures by business segments									31.1	42.4	39.0
US [Member] | Largest 5 Markets [Member] | Property and Equipment [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization by business segments									49.8	49.1	45.6
US [Member] | Largest 5 Markets [Member] | Intangible assets member [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization by business segments									0	0.2	0.3
France [Member] | Largest 5 Markets [Member]
Segment Reporting Information [Line Items]
Capital expenditures by business segments									17.9	13.8	15.8
France [Member] | Largest 5 Markets [Member] | Property and Equipment [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization by business segments									19.3	22.1	20.6
France [Member] | Largest 5 Markets [Member] | Intangible assets member [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization by business segments									0.3	0.4	0.3
Mexico [Member] | Largest 5 Markets [Member]
Segment Reporting Information [Line Items]
Capital expenditures by business segments									13.3	24.5	27.4
Mexico [Member] | Largest 5 Markets [Member] | Property and Equipment [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization by business segments									19.6	19.2	14.3
Mexico [Member] | Largest 5 Markets [Member] | Intangible assets member [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization by business segments									0	0	0
Brazil [Member] | Largest 5 Markets [Member]
Segment Reporting Information [Line Items]
Capital expenditures by business segments									14.7	13.2	12.4
Brazil [Member] | Largest 5 Markets [Member] | Property and Equipment [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization by business segments									8.8	9.0	8.7
Brazil [Member] | Largest 5 Markets [Member] | Intangible assets member [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization by business segments									1.4	1.7	2.1
Canada [Member] | Largest 5 Markets [Member]
Segment Reporting Information [Line Items]
Capital expenditures by business segments									6.4	9.6	9.1
Canada [Member] | Largest 5 Markets [Member] | Property and Equipment [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization by business segments									8.5	8.3	9.0
Canada [Member] | Largest 5 Markets [Member] | Intangible assets member [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization by business segments									$ 0	$ 0	$ 0