Common Stock Repurchase Plan (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Sep. 21, 2017	Dec. 31, 2016	Sep. 16, 2002
Equity, Class of Treasury Stock [Line Items]
Total number of shares repurchased	2,362,418		2,362,418
Total cost of shares repurchased	$ 1,308,187		$ 1,308,187
2002 Common Stock Repurchase Plan [Member]
Equity, Class of Treasury Stock [Line Items]
Stock repurchase plan, number of shares permitted		3,500,000
Remaining number of shares available to be repurchased		1,154,940
Total number of shares repurchased	2,345,060
Total cost of shares repurchased	$ 1,289,467
Average cost per share repurchased (usd per share)	$ 0.55
Stock Repurchase Programs Prior to 2002 [Member]
Equity, Class of Treasury Stock [Line Items]
Total number of shares repurchased				17,358
Total cost of shares repurchased				$ 18,720