Segment information - Assets, Long Lived Assets, Revnues, Net Assets by Geographic Area (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Segment Reporting Information [Line Items]
Total assets	$ 2,192.2us-gaap_Assets	$ 2,498.0us-gaap_Assets	$ 2,553.9us-gaap_Assets
Long-Lived Assets	669.5us-gaap_NoncurrentAssets	758.7us-gaap_NoncurrentAssets	793.8us-gaap_NoncurrentAssets
Revenues	3,562.3us-gaap_Revenues	3,778.6us-gaap_Revenues	3,577.6us-gaap_Revenues
Assets Net	746.9us-gaap_AssetsNet	912.8us-gaap_AssetsNet	842.6us-gaap_AssetsNet
Largest 5 Markets [Member]
Segment Reporting Information [Line Items]
Total assets	1,088.3	1,124.0	1,144.7
Global Markets [Member]
Segment Reporting Information [Line Items]
Total assets	713.2	1,019.0	1,000.2
Payment Services [Member]
Segment Reporting Information [Line Items]
Total assets	63.7	72.0	27.9
Business Segments [Member]
Segment Reporting Information [Line Items]
Total assets	1,865.2	2,215.0	2,172.8
Corporate Items [Member]
Segment Reporting Information [Line Items]
Total assets	327.0	283.0	381.1
Latin America [Member]
Segment Reporting Information [Line Items]
Assets Net	182.4	273.0	203.6
Latin America [Member] \| Global Markets [Member]
Segment Reporting Information [Line Items]
Total assets	296.0	521.1	418.0
Europe, Middle East and Africa [Member]
Segment Reporting Information [Line Items]
Assets Net	146.1	180.6	192.9
Europe, Middle East and Africa [Member] \| Global Markets [Member]
Segment Reporting Information [Line Items]
Total assets	308.0	382.8	433.9
Asia Pacific [Member]
Segment Reporting Information [Line Items]
Assets Net	69.2	72.7	89.1
Asia Pacific [Member] \| Global Markets [Member]
Segment Reporting Information [Line Items]
Total assets	109.2	115.1	148.3
Non US Region [Member]
Segment Reporting Information [Line Items]
Long-Lived Assets	461.4	539.9	584.3
Revenues	2,833.7	3,071.1	2,870.9
US [Member]
Segment Reporting Information [Line Items]
Long-Lived Assets	208.1	218.8	209.5
Revenues	728.6	707.5	706.7
US [Member] \| Largest 5 Markets [Member]
Segment Reporting Information [Line Items]
Total assets	327.4	330.0	345.2
France [Member]
Segment Reporting Information [Line Items]
Assets Net	96.3	110.8	79.2
France [Member] \| Largest 5 Markets [Member]
Segment Reporting Information [Line Items]
Total assets	244.7	246.6	244.1
France [Member] \| Non US Region [Member]
Segment Reporting Information [Line Items]
Long-Lived Assets	75.7	88.5	94.3
Revenues	517.4	542.5	535.5
Mexico [Member]
Segment Reporting Information [Line Items]
Assets Net	88.4	101.2	131.5
Mexico [Member] \| Largest 5 Markets [Member]
Segment Reporting Information [Line Items]
Total assets	258.9	285.1	269.3
Mexico [Member] \| Non US Region [Member]
Segment Reporting Information [Line Items]
Long-Lived Assets	114.4	136.8	133.7
Revenues	388.5	424.1	395.0
Brazil [Member]
Segment Reporting Information [Line Items]
Assets Net	111.1	105.2	103.1
Brazil [Member] \| Largest 5 Markets [Member]
Segment Reporting Information [Line Items]
Total assets	165.0	165.8	165.7
Brazil [Member] \| Non US Region [Member]
Segment Reporting Information [Line Items]
Long-Lived Assets	47.9	47.6	47.9
Revenues	442.3	392.0	388.3
Canada [Member]
Segment Reporting Information [Line Items]
Assets Net	53.4	69.3	43.2
Canada [Member] \| Largest 5 Markets [Member]
Segment Reporting Information [Line Items]
Total assets	92.3	96.5	120.4
Canada [Member] \| Non US Region [Member]
Segment Reporting Information [Line Items]
Long-Lived Assets	47.9	50.7	68.4
Revenues	179.7	191.4	187.5
Other [Member] \| Non US Region [Member]
Segment Reporting Information [Line Items]
Long-Lived Assets	175.5	216.3	240.0
Revenues	$ 1,305.8	$ 1,521.1	$ 1,364.6

Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.18)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 12

-Article 7

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 18

-Article 5

+ Details

Name:	us-gaap_Assets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of net assets (liabilities).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 946

-SubTopic 225

-Section S99

-Paragraph 3

-Subparagraph (SX 210.6-09.6,7)

-URI http://asc.fasb.org/extlink&oid=6488393&loc=d3e606914-122999

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 205

-SubTopic 30

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=35686370&loc=SL35686385-199418

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 946

-SubTopic 210

-Section S99

-Paragraph 2

-Subparagraph (SX 210.6-05.4)

-URI http://asc.fasb.org/extlink&oid=6488278&loc=d3e604008-122996

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 05

-Paragraph 4

-Article 6

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 09

-Paragraph 19

-Article 6

+ Details

Name:	us-gaap_AssetsNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Long-lived assets other than financial instruments, long-term customer relationships of a financial institution, mortgage and other servicing rights, deferred policy acquisition costs, and deferred tax assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 280

-SubTopic 10

-Section 50

-Paragraph 41

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6534315&loc=d3e9038-108599

+ Details

Name:	us-gaap_NoncurrentAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.1)

-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 1

-Article 5

+ Details

Name:	us-gaap_Revenues
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration