SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Reconciliation of Cash, Cash Equivalents and Restricted Cash (Details) - USD ($)		Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Accounting Policies [Abstract]
Cash and cash equivalents	[1]	$ 42,257,248	$ 34,347,339
Restricted cash	[1]	11,658,225	11,275,263
Total cash, cash equivalents and restricted cash		$ 53,915,473	$ 45,622,602	$ 40,406,476	$ 37,889,596

[1] Our consolidated balance sheets include assets and liabilities of consolidated variable interest entities ("VIEs") as the Company is the primary beneficiary of these VIEs. As of March 31, 2018 and December 31, 2017, assets of consolidated VIEs totaled $1,223,232,702 and $1,255,404,335 respectively, and the liabilities of consolidated VIEs totaled $1,197,735,060 and $1,228,295,517 respectively