Service Providers and Related Party Agreements - Additional Information (Detail) - USD ($)	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Related Party Transactions [Abstract]
Management fee percentage per annum of daily NAV	0.85%
Fee waiver termination notice period	60 days
Managing owner waived fees	$ 98,734	$ 112,573

Amount of fee contractually waived by investment company.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
-SubTopic 20
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=66023616&loc=d3e9046-115832

Name:	us-gaap_InvestmentCompanyContractualFeeWaived
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration