Document And Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2019	Jan. 31, 2020	Jun. 30, 2019
Document Information [Line Items]
Entity Central Index Key	0001332174
Entity Registrant Name	iShares S&P GSCI Commodity-Indexed Trust
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2019
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2019
Document Transition Report	false
Entity File Number	001-32947
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	51-6573369
Entity Address, Address Line One	400 Howard Street
Entity Address, City or Town	San Francisco
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94105
City Area Code	415
Local Phone Number	670-2000
Title of 12(b) Security	Shares
Trading Symbol	GSG
Security Exchange Name	NYSEArca
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float			$ 445,299,343
Entity Common Stock, Shares Outstanding		48,950,000