Segment information - Concentration of revenue by customer by geographical region (Details) - Revenue	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Geographical concentration risk | Multi-currency processing services | APAC | Customer A
Revenue concentration
Concentration risk (as a percent)	59.00%	60.00%
Geographical concentration risk | Multi-currency processing services | Americas | Customer D
Revenue concentration
Concentration risk (as a percent)	27.00%	15.00%
Geographical concentration risk | Multi-currency processing services | Americas | Customer E
Revenue concentration
Concentration risk (as a percent)		14.00%
Geographical concentration risk | Multi-currency processing services | Americas | Customer F
Revenue concentration
Concentration risk (as a percent)	10.00%	18.00%
Geographical concentration risk | Multi-currency processing services | EMEA | Customer C
Revenue concentration
Concentration risk (as a percent)	63.00%	62.00%
Geographical concentration risk | Multi-currency processing services | EMEA | Customer H
Revenue concentration
Concentration risk (as a percent)	35.00%	37.00%
Customer concentration risk | Customer A
Revenue concentration
Concentration risk (as a percent)	17.00%	20.00%
Customer concentration risk | Customer C
Revenue concentration
Concentration risk (as a percent)	12.00%	11.00%
Customer concentration risk | Customer H
Revenue concentration
Concentration risk (as a percent)	11.00%
Customer concentration risk | Multi-currency processing services | Customer B
Revenue concentration
Concentration risk (as a percent)	15.00%	15.00%
Customer concentration risk | Multi-currency processing services | Customer G
Revenue concentration
Concentration risk (as a percent)	28.00%	19.00%