QUARTERLY RESULTS OF OPERATIONS (UNAUDITED) (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
QUARTERLY RESULTS OF OPERATIONS (UNAUDITED)
Revenue (Note 7)	$ 119,965	$ 136,437	$ 123,643	$ 118,774	$ 115,694	$ 109,778	$ 97,592	$ 99,992	$ 498,819	$ 423,056	$ 459,042
Operating income	44,576	52,281	53,307	48,781	40,724	43,201	31,449	25,333	198,945	140,707	(74,535)
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)
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)