Note 9 - Investing in Index Futures (Details Textual) - USD ($)	3 Months Ended	12 Months Ended
Mar. 31, 2020	Dec. 31, 2019
Average Month-End Notional Amount of Derivative Contracts	$ 672,663,538	$ 960,422,151

Average month end notional amount specified by the derivative contracts.

No definition available.

Name:	gsg_AverageMonthEndNotionalAmountOfDerivativeContracts
Namespace Prefix:	gsg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration