Schedule II-Valuation and Qualifying Accounts (Details) (Reserve deducted from assets: accumulated provision for uncollectible accounts., USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Reserve deducted from assets: accumulated provision for uncollectible accounts.
Valuation and Qualifying Accounts
Balance At Beginning Of Period	$ 1,137,644	$ 865,236	$ 1,086,853
Charged To Income	3,052,397	3,737,630	3,607,066
Charged to Other Accounts	1,956,549	1,847,527	833,113
Deductions From Reserve	4,758,917	5,312,749	4,661,796
Balance At Close of Period	$ 1,387,673	$ 1,137,644	$ 865,236