REVENUE - Metal Disaggregation (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Disaggregation of Revenue
Revenue	$ 136,437	$ 109,778	$ 378,853	$ 307,362
Stream interests
Disaggregation of Revenue
Revenue	97,460	77,765	274,065	215,480
Stream interests | Gold
Disaggregation of Revenue
Revenue	78,503	62,856	219,838	175,149
Stream interests | Silver
Disaggregation of Revenue
Revenue	8,284	7,908	25,648	24,512
Stream interests | Copper
Disaggregation of Revenue
Revenue	10,673	7,001	28,579	15,819
Royalty interests
Disaggregation of Revenue
Revenue	38,977	32,013	104,788	91,882
Royalty interests | Gold
Disaggregation of Revenue
Revenue	28,792	22,041	72,617	60,251
Royalty interests | Silver
Disaggregation of Revenue
Revenue	2,666	1,608	7,860	4,527
Royalty interests | Copper
Disaggregation of Revenue
Revenue	3,340	3,056	10,427	11,030
Royalty interests | Other
Disaggregation of Revenue
Revenue	$ 4,179	$ 5,308	$ 13,884	$ 16,074