v3.8.0.1
Document and Entity Information - shares
3 Months Ended
Apr. 30, 2018
Jun. 01, 2018
Document And Entity Information [Abstract]    
Document Type 10-Q  
Amendment Flag false  
Document Period End Date Apr. 30, 2018  
Document Fiscal Year Focus 2019  
Document Fiscal Period Focus Q1  
Trading Symbol AMBA  
Entity Registrant Name AMBARELLA INC  
Entity Central Index Key 0001280263  
Current Fiscal Year End Date --01-31  
Entity Filer Category Large Accelerated Filer  
Entity Common Stock, Shares Outstanding   33,410,455