REVENUE - Metal Disaggregation (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2018
Disaggregation of Revenue
Revenue	$ 123,643	$ 97,592	$ 242,417	$ 197,585
Stream interests
Disaggregation of Revenue
Revenue	89,625	67,679	176,606	137,716
Stream interests | Gold
Disaggregation of Revenue
Revenue	69,111	53,179	141,335	112,293
Stream interests | Silver
Disaggregation of Revenue
Revenue	8,929	7,884	17,365	16,604
Stream interests | Copper
Disaggregation of Revenue
Revenue	11,585	6,616	17,906	8,819
Royalty interests
Disaggregation of Revenue
Revenue	34,018	29,913	65,811	59,869
Royalty interests | Gold
Disaggregation of Revenue
Revenue	22,068	19,656	43,825	38,210
Royalty interests | Silver
Disaggregation of Revenue
Revenue	3,365	1,567	5,194	2,919
Royalty interests | Copper
Disaggregation of Revenue
Revenue	4,107	4,359	7,087	7,974
Royalty interests | Other
Disaggregation of Revenue
Revenue	$ 4,478	$ 4,331	$ 9,705	$ 10,766