EARNINGS PER SHARE ("EPS") (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2018
EARNINGS PER SHARE ("EPS")
Net income (loss) available to Royal Gold common stockholders	$ 49,015	$ 38,554	$ 41,321	$ 70,453	$ 26,459	$ 28,772	$ 23,586	$ 15,008	$ 199,343	$ 93,825	$ (113,134)
Net income and comprehensive income available to Royal Gold common stockholders									$ 199,343	$ 93,825	$ (115,214)
Weighted-average shares for basic EPS									65,523,024	65,394,627	65,291,855
Effect of other dilutive securities (in shares)									120,366	110,908
Weighted-average shares for diluted EPS									65,643,390	65,505,535	65,291,855
Basic earnings (loss) per share (in dollars per share)	$ 0.75	$ 0.59	$ 0.63	$ 1.07	$ 0.40	$ 0.44	$ 0.36	$ 0.23	$ 3.04	$ 1.43	$ (1.73)
Diluted earnings (loss) per share (in dollars per share)	$ 0.75	$ 0.59	$ 0.63	$ 1.07	$ 0.40	$ 0.44	$ 0.36	$ 0.23	$ 3.03	$ 1.43	$ (1.73)