Schedule II-Valuation and Qualifying Accounts (Details) - Allowance for Doubtful Accounts [Member] - USD ($)		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of period		$ 390,000	$ 420,000	$ 420,000
Charged to costs and expenses		833,271	811,528	873,269
Deductions	[1]	813,271	841,528	873,269
Balance at end of period		$ 410,000	$ 390,000	$ 420,000

[1] Charges to the account are for the purpose for which the reserves were created.