EARNINGS PER SHARE ("EPS") (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2016
Net (loss) income attributable to Royal Gold stockholders	$ 26,650	$ (153,650)	$ (14,765)	$ 28,631	$ 20,020	$ 23,661	$ 28,062	$ 29,787	$ (113,134)	$ 101,530	$ (77,149)
Weighted-average shares for basic EPS									65,291,855	65,152,782	65,074,455
Effect of other dilutive securities (in shares)										125,171
Weighted-average shares for diluted EPS									65,291,855	65,277,953	65,074,455
Basic (loss) earnings per share (in dollars per share)	$ 0.41	$ (2.35)	$ (0.23)	$ 0.44	$ 0.31	$ 0.36	$ 0.43	$ 0.46	$ (1.73)	$ 1.55	$ (1.18)
Diluted (loss) earnings per share (in dollars per share)	0.41	$ (2.35)	$ (0.23)	$ 0.44	$ 0.31	$ 0.36	$ 0.43	$ 0.46	$ (1.73)	$ 1.55	$ (1.18)
2019 Notes
Dilutive effect of conversion of debt securities									0
Initial conversion price (in dollars per share)	$ 102.91								$ 102.91