STREAM AND ROYALTY INTERESTS, NET - Impairments (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Jun. 30, 2020	Jun. 30, 2020	Jun. 30, 2018	Jun. 30, 2019
Impairments of royalty and stream interests			$ 1,341	$ 239,364
Stream and royalty interests, net		$ 2,318,913	2,318,913		$ 2,339,316
Royalty interests
Impairments of royalty and stream interests			1,341	239,364
Stream and royalty interests, net		704,550	704,550		$ 716,881
Pascua-Lama
Impairments of royalty and stream interests	$ 239,100
Stream and royalty interests, net		177,700	$ 177,700
Copper NSR (as a percent)			1.09%
Pascua-Lama | Minimum
Net smelter return (NSR) (as a percent)			0.78%
Pascua-Lama | Maximum
Net smelter return (NSR) (as a percent)			5.45%
Pascua-Lama | Royalty interests
Impairments of royalty and stream interests				239,080
Other | Royalty interests
Impairments of royalty and stream interests			$ 1,341	$ 284
El Toqui
Impairments of royalty and stream interests		1,300
Stream and royalty interests, net		$ 0	$ 0