REVENUE - Property Disaggregation (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2020	Dec. 31, 2019
Disaggregation of Revenue
Revenue	$ 158,360	$ 123,643	$ 305,240	$ 242,417
Stream interests
Disaggregation of Revenue
Revenue	107,719	89,625	214,222	176,606
Stream interests | Mount Milligan
Disaggregation of Revenue
Revenue	44,713	30,629	79,332	61,126
Stream interests | Pueblo Viejo
Disaggregation of Revenue
Revenue	27,554	23,614	58,824	45,232
Stream interests | Andacollo
Disaggregation of Revenue
Revenue	17,766	20,665	41,275	41,269
Stream interests | Wassa and Prestea
Disaggregation of Revenue
Revenue	6,761	4,794	15,870	10,113
Stream interests | Other
Disaggregation of Revenue
Revenue	10,925	9,923	18,921	18,866
Royalty interests
Disaggregation of Revenue
Revenue	50,641	34,018	91,018	65,811
Royalty interests | Other
Disaggregation of Revenue
Revenue	29,561	23,149	54,045	46,105
Royalty interests | Penasquito
Disaggregation of Revenue
Revenue	12,952	7,577	23,161	11,997
Royalty interests | Cortez
Disaggregation of Revenue
Revenue	$ 8,128	$ 3,292	$ 13,812	$ 7,709