Schedule II-Valuation and Qualifying Accounts (Details) (Reserve deducted from assets: accumulated provision for uncollectible accounts., USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Reserve deducted from assets: accumulated provision for uncollectible accounts.
Valuation and Qualifying Accounts
Balance At Beginning Of Period	$ 865,236	$ 1,086,853	$ 1,265,421
Charged To Income	3,737,630	3,607,066	3,109,679
Charged to Other Accounts	1,847,527	833,113	1,531,820
Deductions From Reserve	5,312,749	4,661,796	4,820,067
Balance At Close of Period	$ 1,137,644	$ 865,236	$ 1,086,853