SEGMENT INFORMATION (Details) $ in Thousands	3 Months Ended
	Sep. 30, 2020 USD ($) segment	Sep. 30, 2019 USD ($)	Jun. 30, 2020 USD ($)
Long Lived Assets and Pre-Tax Income by Geographical Information
Number of reportable segments | segment	2
Stream and royalty interests, net	$ 2,242,314		$ 2,318,913
Revenue	146,880	$ 118,774
Cost of sales	21,902	20,111
Production taxes	1,355	1,099
Depletion	46,214	38,661
Total segment gross profit	77,409	58,903
Canada
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	871,417		892,587
Dominican Republic
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	394,580		406,469
Chile
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	495,970		501,583
Africa
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	223,836		215,784
Mexico
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	74,273		75,951
United States
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	116,723		159,445
Australia
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	29,649		30,006
Rest of world
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	35,866		37,088
Stream interests
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	1,586,446		1,614,363
Revenue	106,503	86,981
Cost of sales	21,902	20,111
Depletion	39,027	31,462
Total segment gross profit	45,574	35,408
Stream interests | Canada
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	684,459		702,732
Revenue	41,586	37,663
Stream interests | Dominican Republic
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	394,580		406,469
Revenue	31,270	21,618
Stream interests | Chile
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	271,854		277,661
Revenue	23,509	20,604
Stream interests | Africa
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	223,515		215,463
Revenue	10,138	7,096
Stream interests | Rest of world
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	12,038		12,038
Royalty interests
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	655,868		704,550
Revenue	40,377	31,793
Production taxes	1,355	1,099
Depletion	7,187	7,199
Total segment gross profit	31,835	23,495
Royalty interests | Canada
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	186,958		189,855
Revenue	7,410	8,921
Royalty interests | Chile
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	224,116		223,922
Royalty interests | Africa
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	321		321
Revenue	750	470
Royalty interests | Mexico
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	74,273		75,951
Revenue	11,577	6,387
Royalty interests | United States
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	116,723		159,445
Revenue	13,698	10,602
Royalty interests | Australia
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	29,649		30,006
Revenue	4,542	3,802
Royalty interests | Rest of world
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	23,828		$ 25,050
Revenue	$ 2,400	$ 1,611