Note 3 - Offering of the Shares (Details Textual)	Dec. 31, 2018 shares
Shares Prescribed Aggregation	50,000

Prescribed aggregation at which shares are issued and redeemed.

No definition available.

Name:	gsg_SharesPrescribedAggregation
Namespace Prefix:	gsg_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant