Note 3 - Offering of the Shares (Details)	Sep. 30, 2015 shares
Stockholders' Equity Note [Abstract]
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