Statements of Financial Condition (Unaudited) (Parenthetical) - USD ($)	Sep. 30, 2018	Dec. 31, 2017
Investments in Securities, cost	$ 30,228,850	$ 40,033,382
US Treasury Bill Securities [Member]
Investments in Securities, cost	$ 27,862,733	$ 37,938,272

Cost of the investment.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
-SubTopic 210
-Section 50
-Paragraph 6
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=99383244&loc=d3e12121-115841

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant