v2.4.0.8
Document And Entity Information
9 Months Ended
Sep. 30, 2014
Nov. 10, 2014
Document and Entity Information [Abstract]    
Entity Registrant Name Amphastar Pharmaceuticals, Inc.  
Document Type 10-Q  
Current Fiscal Year End Date --12-31  
Entity Common Stock, Shares Outstanding   44,648,798
Amendment Flag false  
Entity Central Index Key 0001297184  
Entity Current Reporting Status Yes  
Entity Voluntary Filers No  
Entity Filer Category Non-accelerated Filer  
Entity Well-known Seasoned Issuer No  
Document Period End Date Sep. 30, 2014  
Document Fiscal Year Focus 2014  
Document Fiscal Period Focus Q3