v3.19.3
Cover Page - shares
9 Months Ended
Sep. 30, 2019
Nov. 04, 2019
Class of Stock [Line Items]    
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Sep. 30, 2019  
Document Transition Report false  
Entity File Number 001-38434  
Entity Registrant Name Dropbox, Inc.  
Entity Central Index Key 0001467623  
Current Fiscal Year End Date --12-31  
Document Fiscal Year Focus 2019  
Document Fiscal Period Focus Q3  
Amendment Flag false  
Entity Incorporation, State or Country Code DE  
Entity Tax Identification Number 26-0138832  
Entity Address, Address Line One 1800 Owens Street  
Entity Address, City or Town San Francisco  
Entity Address, State or Province CA  
Entity Address, Postal Zip Code 94158  
City Area Code 415  
Local Phone Number 857-6800  
Title of 12(b) Security Class A Common Stock, par value $0.00001 per share  
Trading Symbol DBX  
Security Exchange Name NASDAQ  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Non-accelerated Filer  
Entity Small Business false  
Entity Emerging Growth Company false  
Entity Shell Company false  
Class A common stock    
Class of Stock [Line Items]    
Entity Common Stock, Shares Outstanding   253,940,063
Class B common stock    
Class of Stock [Line Items]    
Entity Common Stock, Shares Outstanding   161,382,933
Class C common stock    
Class of Stock [Line Items]    
Entity Common Stock, Shares Outstanding   0