REVENUE - Disaggregation (Details) $ in Thousands	3 Months Ended
	Sep. 30, 2018 USD ($) item	Sep. 30, 2017 USD ($)
Disaggregation of Revenue
Number of revenue sources | item	2
Royalty Revenue	$ 99,992	$ 112,476
Stream interest
Disaggregation of Revenue
Royalty Revenue	70,037	78,762
Stream interest | Andacollo
Disaggregation of Revenue
Royalty Revenue	27,743
Stream interest | Pueblo Viejo
Disaggregation of Revenue
Royalty Revenue	19,486
Stream interest | Mount Milligan
Disaggregation of Revenue
Royalty Revenue	8,847
Stream interest | Wassa and Prestea
Disaggregation of Revenue
Royalty Revenue	8,061
Stream interest | Other
Disaggregation of Revenue
Royalty Revenue	5,900
Stream interest | Gold
Disaggregation of Revenue
Royalty Revenue	59,114
Stream interest | Silver
Disaggregation of Revenue
Royalty Revenue	8,720
Stream interest | Copper
Disaggregation of Revenue
Royalty Revenue	2,203
Royalty interest
Disaggregation of Revenue
Royalty Revenue	29,955	$ 33,714
Royalty interest | Penasquito
Disaggregation of Revenue
Royalty Revenue	3,637
Royalty interest | Cortez
Disaggregation of Revenue
Royalty Revenue	603
Royalty interest | Other
Disaggregation of Revenue
Royalty Revenue	25,715
Royalty interest | Gold
Disaggregation of Revenue
Royalty Revenue	18,554
Royalty interest | Silver
Disaggregation of Revenue
Royalty Revenue	1,352
Royalty interest | Copper
Disaggregation of Revenue
Royalty Revenue	3,615
Royalty interest | Other Metals
Disaggregation of Revenue
Royalty Revenue	$ 6,434