QUALIFYING ACCOUNTS (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Valuation and Qualifying Accounts
Balance at Beginning of Period	$ 523,004	$ 372,828
Additions, Charged to Costs and Expenses		365,746
Deductions		215,570
Balance at end of Period		523,004	$ 372,828
Allowance for doubtful accounts
Valuation and Qualifying Accounts
Balance at Beginning of Period	523,004	372,828	366,105
Additions, Charged to Costs and Expenses	422,109		201,622
Deductions	301,123		194,899
Balance at end of Period	$ 643,990	$ 523,004	$ 372,828