Summary of significant accounting policies (Details 4) (USD $)	12 Months Ended
	Dec. 31, 2013 item	Dec. 31, 2012	Dec. 31, 2011
Summary of significant accounting policies
Number of stock-based compensation programs	2
Stock-based compensation expense and assumptions
Total stock-based compensation expense	$ 1,227,369	$ 1,135,047	$ 570,810
Capitalized stock-based compensation	52,133
Stock options
Stock-based compensation expense and assumptions
Options granted (in shares)	949,300
Fair value of options granted	1,000,000
Total stock-based compensation expense	983,810	1,135,047	555,882
Capitalized stock-based compensation	100,000	100,000
Unamortized stock-based compensation expense	1,263,133	1,383,725
Weighted average remaining amortization period	1 year 9 months 14 days	1 year 9 months 18 days
Warrants
Stock-based compensation expense and assumptions
Total stock-based compensation expense			14,928
Restricted stock awards
Stock-based compensation expense and assumptions
Stock granted (in shares)	875,583
Fair value of awards granted	1,900,000
Total stock-based compensation expense	243,559
Unamortized stock-based compensation expense	1,624,187
Weighted average remaining amortization period	2 years 18 days
Processing and service costs
Stock-based compensation expense and assumptions
Total stock-based compensation expense	238,101	262,775	135,444
Selling, general and administrative expenses
Stock-based compensation expense and assumptions
Total stock-based compensation expense	$ 989,268	$ 872,272	$ 435,366