Schedule II - Valuation and Qualifying Accounts (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Valuation and Qualifying Accounts [Roll Forward]
Balance at beginning of period	$ 4,816,118	$ 4,100,333	$ 4,588,675
Charged to costs and expenses	2,373,342	2,825,300	2,174,729
Charged to other accounts	37,200	44,400	49,500
Net accounts written off	(2,256,949)	(2,153,915)	(2,712,571)
Balance at end of period	$ 4,969,711	$ 4,816,118	$ 4,100,333