Document and Entity Information	3 Months Ended
	Mar. 31, 2014	May 01, 2014
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2014
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	Q1
Trading Symbol	STEM
Entity Registrant Name	STEMCELLS INC
Entity Central Index Key	0000883975
Current Fiscal Year End Date	--12-31
Entity Filer Category	Smaller Reporting Company
Entity Common Stock, Shares Outstanding		55,514,404