REVENUE - Property Disaggregation (Details) - USD ($) $ in Thousands	3 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Disaggregation of Revenue
Revenue	$ 146,880	$ 118,774
Stream interests
Disaggregation of Revenue
Revenue	106,503	86,981
Stream interests | Mount Milligan
Disaggregation of Revenue
Revenue	34,620	30,497
Stream interests | Pueblo Viejo
Disaggregation of Revenue
Revenue	31,270	21,618
Stream interests | Andacollo
Disaggregation of Revenue
Revenue	23,509	20,604
Stream interests | Wassa and Prestea
Disaggregation of Revenue
Revenue	9,108	5,319
Stream interests | Other
Disaggregation of Revenue
Revenue	7,996	8,943
Royalty interests
Disaggregation of Revenue
Revenue	40,377	31,793
Royalty interests | Other
Disaggregation of Revenue
Revenue	24,484	22,956
Royalty interests | Penasquito
Disaggregation of Revenue
Revenue	10,209	4,420
Royalty interests | Cortez
Disaggregation of Revenue
Revenue	$ 5,684	$ 4,417