Schedule of changes in common stock options (Details) (USD $)	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Options, Outstanding at beginning of year (in shares)	3,898,198	3,141,198
Options, Granted (in shares)	200,000	1,040,000
Options, Exercised (in shares)	(30,000)	(21,750)
Options, Forfeited (in shares)	0	(250,000)
Options, Expired (in shares)	(3,198)	(1,250)
Options, Outstanding at end of quarter (in shares)	4,065,000	3,908,198
Options exercisable at end of quarter (in shares)	2,030,000	1,283,198
Weighted Average Exercise Price, Outstanding at beginning of year (in dollars per share)	$ 1.75	$ 1.65
Weighted Average Exercise Price, Granted (in dollars per share)	$ 1.00	$ 2.04
Weighted Average Exercise Price, Exercised	$ 0.51	$ 0.63
Weighted Average Exercise Price, Expired	$ 2.40	$ 1.40
Weighted Average Exercise Price, Forfeited		$ 1.83
Weighted Average Exercise Price, Outstanding at end of quarter (in dollars per share)	$ 1.72	$ 1.75
Weighted Average Exercise Price, Options exercisable at end of quarter (in dollars per share)	$ 1.59	$ 1.37