Quarterly report pursuant to sections 13 or 15(d)

Document and Entity Information

v2.4.0.8
Document and Entity Information
9 Months Ended
Sep. 30, 2013
Oct. 31, 2013
Document Information [Line Items]    
Document Type 10-Q/A  
Amendment Flag false  
Document Period End Date Sep. 30, 2013  
Document Fiscal Year Focus 2013  
Document Fiscal Period Focus Q3  
Entity Registrant Name CymaBay Therapeutics, Inc.  
Entity Central Index Key 0001042074  
Current Fiscal Year End Date --12-31  
Entity Filer Category Smaller Reporting Company  
Entity Common Stock, Shares Outstanding   9,455,064