Segment information - Information about revenue, profit and assets (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($) item	Jun. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)
Segment information
Number of reportable segments | item			2
Cost of sales included in processing and services costs	$ 3,205,246	$ 3,524,123	$ 6,397,319	$ 7,024,791
Long-lived assets	6,700,000		$ 6,700,000		$ 7,000,000
Number of geographical regions in which the entity conducts its business | item			3
Net Revenue:
Net revenue	12,516,383	13,103,376	$ 25,245,268	26,787,889
Gross Profit:
Total gross profit	7,225,692	6,844,564	14,646,895	14,337,185
Income from operations before provision for income taxes:
Total gross profit	7,225,692	6,844,564	14,646,895	14,337,185
Selling, general and administrative expenses	4,681,705	5,204,892	9,969,043	10,685,606
Restructuring charges	7,284	125,268	72,742	125,268
Income from operations	2,536,703	1,514,404	4,605,110	3,526,311
Interest expense	(92,813)	(83,021)	(209,145)	(97,697)
Interest income	585	398	1,108	822
Total other expense, net	(92,228)	(82,623)	(208,037)	(96,875)
Income from operations before provision for income taxes	2,444,475	1,431,781	4,397,073	3,429,436
Operating segments
Gross Profit:
Total gross profit	9,954,245	9,745,551	20,053,723	19,998,418
Income from operations before provision for income taxes:
Total gross profit	9,954,245	9,745,551	20,053,723	19,998,418
Corporate allocated cost of sales
Gross Profit:
Total gross profit	2,728,553	2,900,987	5,406,828	5,661,233
Income from operations before provision for income taxes:
Total gross profit	2,728,553	2,900,987	5,406,828	5,661,233
Multi-currency processing services
Segment information
Cost of sales included in processing and services costs	500,000	600,000	1,000,000	1,400,000
Net Revenue:
Net revenue	8,510,966	7,958,606	16,943,870	16,592,838
Multi-currency processing services | Operating segments
Gross Profit:
Total gross profit	8,034,273	7,335,470	15,953,379	15,229,280
Income from operations before provision for income taxes:
Total gross profit	8,034,273	7,335,470	15,953,379	15,229,280
Payment processing services
Net Revenue:
Net revenue	4,005,417	5,144,770	8,301,398	10,195,051
Payment processing services | Operating segments
Gross Profit:
Total gross profit	1,919,972	2,410,081	4,100,344	4,769,138
Income from operations before provision for income taxes:
Total gross profit	1,919,972	2,410,081	4,100,344	4,769,138
APAC
Net Revenue:
Net revenue	4,143,965	3,761,918	8,237,350	7,578,982
APAC | Multi-currency processing services | Operating segments
Gross Profit:
Total gross profit	4,118,537	3,731,646	8,191,331	7,525,150
Income from operations before provision for income taxes:
Total gross profit	4,118,537	3,731,646	8,191,331	7,525,150
The Americas
Net Revenue:
Net revenue	3,226,629	2,444,187	6,195,781	4,629,561
The Americas | Multi-currency processing services | Operating segments
Gross Profit:
Total gross profit	3,001,927	2,261,907	5,798,823	4,296,595
Income from operations before provision for income taxes:
Total gross profit	3,001,927	2,261,907	5,798,823	4,296,595
EMEA
Net Revenue:
Net revenue	1,140,372	1,752,501	2,510,739	4,384,295
EMEA | Multi-currency processing services | Operating segments
Gross Profit:
Total gross profit	913,809	1,341,917	1,963,225	3,407,535
Income from operations before provision for income taxes:
Total gross profit	$ 913,809	$ 1,341,917	$ 1,963,225	$ 3,407,535