Stockholders' Equity (Stock Option Transactions) (Details) - Options [Member] - $ / shares	12 Months Ended
	Dec. 31, 2018		Dec. 31, 2017	Dec. 31, 2016
Number of shares
Outstanding, Beginning balance	4,339,443		4,166,943	3,629,693
Granted to employees, officers, directors and others	969,000	[1]	2,212,500	2,265,000
Expired/Cancelled/Forfeited	(237,500)		(360,000)	(172,250)
Exercised	(282,500)		(1,680,000)	(1,555,500)
Outstanding, Ending balance	4,788,443		4,339,443	4,166,943
Number of shares Exercisable	4,788,443		4,319,443
Weighted average exercise price
Outstanding, Beginning balance	$ 1.37		$ 1.58	$ 1.76
Granted to employees, officers, directors and others	1.11	[1]	0.34	0.27
Expired/Cancelled/Forfeited	1.75		2.32	2.76
Exercised	0.07		0.33	0.01
Outstanding, Ending balance	1.37		1.37	$ 1.58
Weighted Average exercise price Exercisable	$ 1.38		$ 1.37

[1] The receipt of a stock option grant by the grantee recipient is a non-taxable event according to the Internal Revenue Service. The grantee who later chooses to exercise penny stock options must recognize the market value in income in the year of exercise.