Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2019	May 06, 2019
Document Information [Line Items]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q1
Entity Registrant Name	United States Commodity Index Funds Trust
Entity Central Index Key	0001479247
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Trading Symbol	USCI
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Common Stock, Shares Outstanding		11,550,000
United States Commodity Index Fund [Member]
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		10,700,000
United States Copper Index Fund [Member]
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		850,000