Document And Entity Information - shares	9 Months Ended
	Sep. 30, 2021	Oct. 20, 2021
Document Information
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2021
Document Transition Report	false
Entity File Number	001-34833
Entity Registrant Name	United States Commodity Index Funds Trust
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	27-1537655
Entity Address, Address Line One	1850 Mt. Diablo Boulevard, Suite 640
Entity Address, City or Town	Walnut Creek
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94596
City Area Code	510
Local Phone Number	522-9600
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 Central Index Key	0001479247
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q3
Amendment Flag	false
Common Stock
Document Information
Entity Common Stock, Shares Outstanding		14,900,000
United States Commodity Index Fund
Document Information
Title of 12(b) Security	Shares of United States Commodity Index Fund
Trading Symbol	USCI
Security Exchange Name	NYSEArca
Entity Common Stock, Shares Outstanding		5,900,000
United States Copper Index Fund
Document Information
Title of 12(b) Security	Shares of United States Copper Index Fund
Trading Symbol	CPER
Security Exchange Name	NYSEArca
Entity Common Stock, Shares Outstanding		9,000,000