Accounts Receivable (Details) (USD $)	Dec. 31, 2012	Dec. 31, 2011
Components of accounts receivable
Accounts receivable	$ 12,670,680	$ 9,706,566
Less: allowance for doubtful accounts	(2,592,057)	(2,618,608)
Accounts receivable, net	$ 10,078,623	$ 7,087,958