SUBSEQUENT EVENTS (Details) - Contango - $ / shares	Oct. 03, 2018	Sep. 30, 2018
Subsequent events
Investment shares owned (in shares)		682,556
Subsequent Event
Subsequent events
Shares purchased (in shares)	127,188
Price per purchased share (in dollars per share)	$ 26
Investment shares owned (in shares)	809,744

Balance held at close of period in number of shares.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant