v3.10.0.1
Document and Entity Information - USD ($)
12 Months Ended
Jun. 30, 2018
Aug. 01, 2018
Dec. 31, 2017
Document and Entity Information      
Entity Registrant Name ROYAL GOLD INC    
Entity Central Index Key 0000085535    
Document Type 10-K    
Document Period End Date Jun. 30, 2018    
Amendment Flag false    
Current Fiscal Year End Date --06-30    
Entity Well-known Seasoned Issuer Yes    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Filer Category Large Accelerated Filer    
Entity Public Float     $ 5,335,748,560
Entity Shares Outstanding   65,505,110  
Document Fiscal Year Focus 2018    
Document Fiscal Period Focus FY