v3.7.0.1
Document and Entity Information - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2016
Mar. 03, 2017
Oct. 28, 2016
Document And Entity Information [Abstract]      
Document Type 10-K    
Amendment Flag false    
Document Period End Date Dec. 31, 2016    
Document Fiscal Year Focus 2016    
Document Fiscal Period Focus FY    
Trading Symbol BL    
Entity Registrant Name BLACKLINE, INC.    
Entity Central Index Key 0001666134    
Current Fiscal Year End Date --12-31    
Entity Well-known Seasoned Issuer No    
Entity Current Reporting Status Yes    
Entity Voluntary Filers No    
Entity Filer Category Non-accelerated Filer    
Entity Common Stock, Shares Outstanding   51,283,364  
Entity Public Float     $ 261.3