QUARTERLY RESULTS OF OPERATIONS (UNAUDITED) (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
QUARTERLY RESULTS OF OPERATIONS (UNAUDITED)
Revenue	$ 115,694	$ 109,778	$ 97,592	$ 99,992	$ 116,235	$ 115,983	$ 114,348	$ 112,476	$ 423,056	$ 459,042	$ 440,814
Operating income (loss)	40,724	43,201	31,449	25,333	36,247	(193,464)	40,962	41,720	140,707	(74,535)	145,942
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
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