Note 4 - Trust Expenses (Details Textual)	12 Months Ended
Dec. 31, 2018 USD ($)
Sponsors Fee Annualized Accrual Rate Based on Net Asset Value of Trust	0.75%
Maximum [Member]
Legal Fees Per Year Maximum	$ 100,000

Annualized sponsor's fee rate accrued daily based on the net asset value of the trust.

No definition available.

Name:	gsg_SponsorsFeeAnnualizedAccrualRateBasedOnNetAssetValueOfTrust
Namespace Prefix:	gsg_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant