Distribution of Profits (Details) (USD $)
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Distribution of Profits    
Minimum percentage of after-tax profits of PRC subsidiaries and VIEs set aside to fund a statutory reserve 10.00%  
Statutory reserve as a percentage of registered capital up to which after-tax profit of PRC subsidiaries and VIEs shall be transferred to statutory reserve 50.00%  
Statutory reserve fund $ 40,478,568 $ 35,633,687
Restricted portion of net assets, including general reserve and registered capital of PRC subsidiaries and VIEs 183,740,692 174,046,356
Restricted portion of net assets attributed to general reserve and registered capital of the VIEs $ 12,076,642 $ 9,977,982