v3.8.0.1
Document and Entity Information
12 Months Ended
Dec. 31, 2017
shares
Document Information [Line Items]  
Document Type 20-F
Amendment Flag false
Document Period End Date Dec. 31, 2017
Document Fiscal Year Focus 2017
Document Fiscal Period Focus FY
Trading Symbol VNET
Entity Registrant Name 21VIANET GROUP, INC.
Entity Central Index Key 0001508475
Current Fiscal Year End Date --12-31
Entity Well-known Seasoned Issuer No
Entity Current Reporting Status Yes
Entity Filer Category Accelerated Filer
Class A Ordinary Shares  
Document Information [Line Items]  
Entity Common Stock, Shares Outstanding 496,636,128
Class B Ordinary Shares  
Document Information [Line Items]  
Entity Common Stock, Shares Outstanding 174,649,638