EARNINGS PER SHARE ("EPS") (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2017
EARNINGS PER SHARE ("EPS")
Net income (loss) available to Royal Gold common stockholders	$ 26,459	$ 28,772	$ 23,586	$ 15,008	$ 26,650	$ (153,650)	$ (14,765)	$ 28,631	$ 93,825	$ (113,134)	$ 101,530
Weighted-average shares for basic EPS									65,394,627	65,291,855	65,152,782
Effect of other dilutive securities (in shares)									110,908		125,171
Weighted-average shares for diluted EPS									65,505,535	65,291,855	65,277,953
Basic earnings (loss) per share (in dollars per share)	$ 0.40	$ 0.44	$ 0.36	$ 0.23	$ 0.41	$ (2.35)	$ (0.23)	$ 0.44	$ 1.43	$ (1.73)	$ 1.55
Diluted earnings (loss) per share (in dollars per share)	$ 0.40	$ 0.44	$ 0.36	$ 0.23	$ 0.41	$ (2.35)	$ (0.23)	$ 0.44	$ 1.43	$ (1.73)	$ 1.55