v3.26.1
Document and Entity Information - shares
6 Months Ended
Jun. 30, 2026
Jul. 31, 2026
Cover [Abstract]    
Document Type 10-Q  
Amendment Flag false  
Document Period End Date Jun. 30, 2026  
Document Fiscal Year Focus 2026  
Document Fiscal Period Focus Q2  
Trading Symbol RARE  
Entity Registrant Name ULTRAGENYX PHARMACEUTICAL INC.  
Entity Central Index Key 0001515673  
Entity Current Reporting Status Yes  
Current Fiscal Year End Date --12-31  
Entity Filer Category Large Accelerated Filer  
Entity Small Business false  
Entity Emerging Growth Company false  
Entity Common Stock, Shares Outstanding   98,588,873
Entity Shell Company false  
Entity File Number 001-36276  
Entity Tax Identification Number 27-2546083  
Entity Address, Address Line One 60 Leveroni Court  
Entity Address, City or Town Novato  
Entity Address, State or Province CA  
Entity Address, Postal Zip Code 94949  
City Area Code 415  
Local Phone Number 483-8800  
Entity Interactive Data Current Yes  
Title of 12(b) Security Common Stock, $0.001 par value  
Security Exchange Name NASDAQ  
Entity Incorporation, State or Country Code DE  
Document Quarterly Report true  
Document Transition Report false