v2.4.0.8
Document and Entity Information (USD $)
12 Months Ended
Dec. 31, 2014
Feb. 06, 2015
Jun. 30, 2014
Document and Entity Information      
Entity Registrant Name Xencor Inc    
Entity Central Index Key 0001326732    
Document Type 10-K    
Document Period End Date Dec. 31, 2014    
Amendment Flag false    
Current Fiscal Year End Date --12-31    
Entity Well-known Seasoned Issuer No    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Filer Category Accelerated Filer    
Entity Public Float     $ 151,512,499
Entity Common Stock, Shares Outstanding   31,472,763  
Document Fiscal Year Focus 2014    
Document Fiscal Period Focus FY