Condensed Consolidated Statements of Cash Flows (Unaudited) (Parenthetical) - USD ($)	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Statement Of Cash Flows [Abstract]
Cash and cash equivalents	$ 24,969,157	$ 69,597,699	$ 35,556,115
Restricted cash	703,112	1,985,630	2,449,346
Total cash, cash equivalents and restricted cash	$ 25,672,269	$ 71,583,329	$ 38,005,461	$ 27,506,220