Basis of Presentation and Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Restricted cash	$ 6,964,198	$ 8,683,095
Cash denominated in foreign currencies	362,895	977,236
Cash denominated in foreign currencies, proceeds	367,898	$ 984,412
Provision for income tax	0
Uncertain tax position	$ 0
Earliest Tax Year [Member]
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Open tax year	2014
Latest Tax Year [Member]
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Open tax year	2017