Accounts Receivable (Details) (USD $)	Mar. 31, 2013	Dec. 31, 2012
Components of accounts receivable
Accounts receivable	$ 12,076,311	$ 12,670,680
Less: allowance for doubtful accounts	(2,606,294)	(2,592,057)
Accounts receivable, net	$ 9,470,017	$ 10,078,623