Document and Entity Information
Dec. 20, 2019
Document and Entity Information [Abstract]  
Document Type 8-K
Document Period End Date Dec. 20, 2019
Entity File Number 001-36182
Entity Registrant Name XENCOR, INC.
Entity Incorporation, State or Country Code DE
Entity Tax Identification Number 20-1622502
Entity Address, Address Line One 111 West Lemon Avenue
Entity Address, State or Province CA
Entity Address, City or Town Monrovia
Entity Address, Postal Zip Code 91016
City Area Code 626
Local Phone Number 305-5900
Written Communications false
Soliciting Material false
Pre-commencement Tender Offer false
Pre-commencement Issuer Tender Offer false
Title of 12(b) Security Common Stock, par value $0.01 per share
Trading Symbol XNCR
Security Exchange Name NASDAQ
Entity Emerging Growth Company false
Entity Central Index Key 0001326732
Amendment Flag false