Stock-based expense and assumptions (Details) (USD $)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Stock-based expense and assumptions
Total stock-based expense	$ 258,929	$ 224,392
Processing and service costs
Stock-based expense and assumptions
Total stock-based expense	49,643	80,781
Selling, general and administrative expenses
Stock-based expense and assumptions
Total stock-based expense	$ 209,286	$ 143,611