v3.8.0.1
Document and Entity Information - USD ($)
12 Months Ended
Dec. 31, 2017
Jan. 31, 2018
Jun. 30, 2017
Document Information [Line Items]      
Document Type 10-K    
Amendment Flag false    
Document Period End Date Dec. 31, 2017    
Document Fiscal Year Focus 2017    
Document Fiscal Period Focus FY    
Trading Symbol TTD    
Entity Registrant Name TRADE DESK, INC.    
Entity Central Index Key 0001671933    
Current Fiscal Year End Date --12-31    
Entity Well-known Seasoned Issuer Yes    
Entity Current Reporting Status Yes    
Entity Voluntary Filers No    
Entity Filer Category Large Accelerated Filer    
Entity Public Float     $ 1,543,997,839
Class A common stock      
Document Information [Line Items]      
Entity Common Stock, Shares Outstanding   32,695,082  
Class B common stock      
Document Information [Line Items]      
Entity Common Stock, Shares Outstanding   9,155,054