Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Accounting Policies [Abstract]
Distributed earnings	$ 0	$ 0
Average charges paid to broker per round-turn trade, maximum	7.00	$ 9.00
LME contracts receivable	$ 14,199,993		$ 9,571,095
LME contracts receivable			$ 9,571,095

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://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 60B
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121326447&loc=SL5780133-109256

Name:	us-gaap_DistributedEarnings
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration