Document and Entity Information
9 Months Ended
Dec. 31, 2014
Jan. 21, 2015
Document And Entity Information [Abstract]    
Trading Symbol CVLT  
Entity Registrant Name COMMVAULT SYSTEMS INC  
Entity Central Index Key 0001169561  
Current Fiscal Year End Date --03-31  
Entity Filer Category Large Accelerated Filer  
Document Type 10-Q  
Document Period End Date Dec. 31, 2014  
Document Fiscal Year Focus 2015  
Document Fiscal Period Focus Q3  
Amendment Flag false  
Entity Common Stock, Shares Outstanding   44,896,991