v3.25.1
Cover - shares
 3 Months Ended
Mar. 31, 2025
May 02, 2025
Cover [Abstract]    
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Mar. 31, 2025  
Document Transition Report false  
Entity File Number 001-38981  
Entity Registrant Name Mirum Pharmaceuticals, Inc.  
Entity Incorporation, State or Country Code DE  
Entity Tax Identification Number 83-1281555  
Entity Address, Address Line One 989 East Hillsdale Boulevard  
Entity Address, Address Line Two Suite 300  
Entity Address, City or Town Foster City  
Entity Address, State or Province CA  
Entity Address, Postal Zip Code 94404  
City Area Code 650  
Local Phone Number 667-4085  
Title of 12(b) Security Common stock, par value $0.0001 per share  
Trading Symbol MIRM  
Security Exchange Name NASDAQ  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Large Accelerated Filer  
Entity Small Business false  
Entity Emerging Growth Company false  
Entity Shell Company false  
Entity Common Stock, Shares Outstanding   49,534,709
Entity Central Index Key 0001759425  
Document Fiscal Year Focus 2025  
Document Fiscal Period Focus Q1  
Amendment Flag false  
Current Fiscal Year End Date --12-31