REVENUE - Property Disaggregation (Details) - USD ($) $ in Thousands	3 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue
Revenue	$ 118,774	$ 99,992
Stream interests
Disaggregation of Revenue
Revenue	86,981	70,037
Stream interests | Mount Milligan
Disaggregation of Revenue
Revenue	30,497	8,847
Stream interests | Pueblo Viejo
Disaggregation of Revenue
Revenue	21,618	19,486
Stream interests | Andacollo
Disaggregation of Revenue
Revenue	20,604	27,743
Stream interests | Wassa and Prestea
Disaggregation of Revenue
Revenue	5,319	5,325
Stream interests | Rainy River
Disaggregation of Revenue
Revenue	7,166	5,900
Stream interests | Other
Disaggregation of Revenue
Revenue	1,777	2,736
Royalty interests
Disaggregation of Revenue
Revenue	31,793	29,955
Royalty interests | Other
Disaggregation of Revenue
Revenue	22,956	25,715
Royalty interests | Penasquito
Disaggregation of Revenue
Revenue	4,420	3,637
Royalty interests | Cortez
Disaggregation of Revenue
Revenue	$ 4,417	$ 603