Summary of significant accounting policies (Details) (USD $)	3 Months Ended	12 Months Ended
	Sep. 30, 2012	Dec. 31, 2012 item	Dec. 31, 2011	Dec. 31, 2010
Revenue recognition
Number of revenue streams		2
Restricted cash
Multiplier of the daily average of the last thirty days of transactions used to calculate restricted cash balance related to the ACH transaction processing customer required to be held with a sponsor bank		3
Transaction period used to calculate restricted cash balance related to the ACH transaction processing customer required to be held with a sponsor bank		30 days
Allowance for doubtful accounts
Allowance for doubtful accounts		$ 1,500,000	$ 1,400,000
Software licenses impairment
Asset written off to cost of revenue				1,100,000
Goodwill, intangibles and long-lived assets
Amortization period of acquired identifiable intangible assets		5 years
Software development costs and amortization
Capitalized software development costs		4,776,320	4,978,002
Amortization expense		1,700,000	1,500,000	1,100,000
Deferred initial public offering (IPO) costs
Minimum period for which initial public offering is likely to be postponed		90 days
Write-off of deferred IPO costs	2,300,000	2,346,210
Initial public offering costs	$ 2,600,000
Due to merchants
Number of average days for which ACH funds are generally held before payment to merchant		3 days
Minimum
Software development costs and amortization
Estimated useful live		3 years
Maximum
Software development costs and amortization
Estimated useful live		5 years