QUALIFYING ACCOUNTS (Details) - Allowance for doubtful accounts - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Valuation and Qualifying Accounts
Balance at Beginning of Period	$ 240,111	$ 532,161	$ 643,990
Additions, Charged to Costs and Expenses	1,846,237	445,909	357,789
Deductions	632,653	737,959	469,618
Balance at end of Period	$ 1,453,695	$ 240,111	$ 532,161