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 SYNT    
Entity Registrant Name SYNTEL INC    
Entity Central Index Key 0001040426    
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 Large Accelerated Filer    
Entity Common Stock, Shares Outstanding   82,965,154  
Entity Public Float     $ 554,288,060