Document and Entity Information - shares
6 Months Ended
Dec. 31, 2017
Feb. 01, 2018
Document And Entity Information [Abstract]    
Document Type 10-Q  
Amendment Flag false  
Document Period End Date Dec. 31, 2017  
Document Fiscal Year Focus 2018  
Document Fiscal Period Focus Q2  
Trading Symbol MYGN  
Entity Registrant Name MYRIAD GENETICS INC  
Entity Central Index Key 0000899923  
Current Fiscal Year End Date --06-30  
Entity Filer Category Large Accelerated Filer  
Entity Common Stock, Shares Outstanding   69,850,295