Shareholders' Equity - Changes in Shareholders’ Equity (Details) - USD ($)	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	$ 34,252,271	$ 35,864,471	$ 40,585,474	$ 42,451,169	$ 35,864,471	$ 42,451,169
Stock issued	436,613		149,180
Stock-based compensation		426,939	580,603	309,563	863,552
Exercise of stock options	55,743	175,000			230,743
Net loss	(2,651,422)	(2,214,139)	(2,695,792)	(2,175,258)	(4,865,561)	(4,871,050)
Ending balance	32,093,205	34,252,271	38,619,465	40,585,474	32,093,205	38,619,465
Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	39,713	39,613	38,967	38,967	39,613	38,967
Stock issued			398
Exercise of stock options	23	100			123
Ending balance	39,736	39,713	39,365	38,967	39,736	39,365
Treasury Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	(18,929,915)	(18,929,915)	(18,929,915)	(18,929,915)	(18,929,915)	(18,929,915)
Ending balance	(18,929,915)	(18,929,915)	(18,929,915)	(18,929,915)	(18,929,915)	(18,929,915)
Additional paid-in capital
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	96,707,690	96,105,851	94,694,793	94,385,230	96,105,851	94,385,230
Stock issued	436,613		148,782
Stock-based compensation		426,939	580,603	309,563	863,552
Exercise of stock options	55,720	174,900			230,620
Ending balance	97,200,023	96,707,690	95,424,178	94,694,793	97,200,023	95,424,178
Accumulated deficit
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	(43,565,217)	(41,351,078)	(35,218,371)	(33,043,113)	(41,351,078)	(33,043,113)
Net loss	(2,651,422)	(2,214,139)	(2,695,792)	(2,175,258)	(4,865,561)
Ending balance	$ (46,216,639)	$ (43,565,217)	$ (37,914,163)	$ (35,218,371)	$ (46,216,639)	$ (37,914,163)