QUARTERLY RESULTS OF OPERATIONS (UNAUDITED) (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
QUARTERLY RESULTS OF OPERATIONS (UNAUDITED)
Revenue	$ 116,235	$ 115,983	$ 114,348	$ 112,476	$ 108,934	$ 106,972	$ 106,961	$ 117,947	$ 459,042	$ 440,814	$ 359,790
Operating income (loss)	36,247	(193,464)	40,962	41,720	34,619	35,951	34,481	40,891	(74,535)	145,942	4,816
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)
Basic earnings (loss) 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 earnings (loss) 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)