Net income (loss) per share (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Numerator:
Net income (loss)	$ 304,691	$ (1,158,622)	$ 676,607	$ (371,475)
Amounts allocated to participating preferred stockholders under the two-class method	(34,890)		(77,477)
Net income (loss) applicable to common stockholders - basic	269,801	(1,158,622)	599,130	(371,475)
Net income (loss) applicable to common stockholders - diluted	$ 269,801	$ (1,158,622)	$ 599,130	$ (371,475)
Denominator:
Weighted average common stock outstanding (basic) (in shares)	52,832,451	52,035,014	52,805,938	51,906,425
Common equivalent shares from options and warrants to purchase common stock	1,738,025		1,867,034
Weighted average common stock outstanding (diluted) (in shares)	54,570,476	52,035,014	54,672,972	51,906,425
Basic net income (loss) per share applicable to common stockholders (in dollars per share)	$ 0.01	$ (0.02)	$ 0.01	$ (0.01)
Diluted net income (loss) per share applicable to common stockholders (in dollars per share)	$ 0.00	$ (0.02)	$ 0.01	$ (0.01)
Anti-dilutive securities excluded from computation of diluted earnings per share
Total anti-dilutive securities (in shares)	10,443,435	18,014,832	9,503,426	17,329,457
Contingently issued restricted shares | First restricted stock grant
Anti-dilutive securities excluded from computation of diluted earnings per share
Total anti-dilutive securities (in shares)	915,000	915,000	915,000	915,000
Contingently issued restricted shares | Second restricted stock grant
Anti-dilutive securities excluded from computation of diluted earnings per share
Total anti-dilutive securities (in shares)	409,794		409,794
Stock options
Anti-dilutive securities excluded from computation of diluted earnings per share
Total anti-dilutive securities (in shares)	3,532,291	9,055,113	2,592,282	8,369,738
Warrants
Anti-dilutive securities excluded from computation of diluted earnings per share
Total anti-dilutive securities (in shares)	60,000	2,108,575	60,000	2,108,575
Convertible preferred stock
Anti-dilutive securities excluded from computation of diluted earnings per share
Total anti-dilutive securities (in shares)	6,851,144	6,851,144	6,851,144	6,851,144