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Document and Entity Information - USD ($)
 12 Months Ended
Jun. 30, 2019
Aug. 08, 2019
Dec. 31, 2018
Document And Entity Information [Abstract]      
Document Type 10-K    
Amendment Flag false    
Document Period End Date Jun. 30, 2019    
Document Fiscal Year Focus 2019    
Document Fiscal Period Focus FY    
Trading Symbol MYGN    
Entity File Number 0-26642    
Entity Tax Identification Number 870494517    
Entity Address, Address Line One 320 Wakara Way    
Entity Address, City or Town Salt Lake City    
Entity Address, Postal Zip Code 84108    
City Area Code 801    
Local Phone Number 584-3600    
Entity Address, State or Province UT    
Entity Registrant Name MYRIAD GENETICS INC    
Entity Central Index Key 0000899923    
Current Fiscal Year End Date --06-30    
Entity Well-known Seasoned Issuer Yes    
Entity Current Reporting Status Yes    
Entity Voluntary Filers No    
Entity Filer Category Large Accelerated Filer    
Entity Shell Company false    
Entity Small Business false    
Entity Emerging Growth Company false    
Entity Common Stock, Shares Outstanding   73,866,119  
Entity Public Float     $ 2,129,853,783