Summary of Significant Accounting Policies - Schedule of Distributions Per General Share and Share (Detail) - USD ($)	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
General Shares [Member]
Incentive Distribution Made To Managing Member Or General Partner [Line Items]
Distributions per share	$ 0.27586	$ 0.02302
Distributed earnings	$ 9	$ 1
Shares [Member]
Incentive Distribution Made To Managing Member Or General Partner [Line Items]
Distributions per share	$ 0.27586	$ 0.02302
Distributed earnings	$ 5,572,374	$ 538,668

The total amount of dividends declared in the period for each class of stock and the contractual amount of dividends (or interest on participating income bonds) that must be paid for the period (for example, unpaid cumulative dividends). Dividends declared in the current period do not include dividends declared in respect of prior-period unpaid cumulative dividends. Preferred dividends that are cumulative only if earned are deducted only to the extent that they are earned.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 66
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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