SEGMENT INFORMATION (Details) $ in Thousands	3 Months Ended
	Sep. 30, 2019 USD ($) segment	Sep. 30, 2018 USD ($)	Jun. 30, 2019 USD ($)
Long Lived Assets and Pre-Tax Income by Geographical Information
Number of reportable segments | segment	2
Stream and royalty interests, net	$ 2,305,018		$ 2,339,316
Revenue	118,774	$ 99,992
Cost of sales	20,111	16,527
Production taxes	1,099	1,292
Depletion	38,661	42,505
Total segment gross profit	58,903	39,668
Canada
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	953,583		968,000
Dominican Republic
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	441,443		451,585
Chile
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	508,633		515,733
Africa
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	87,231		89,876
Mexico
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	81,920		83,748
United States
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	162,412		163,398
Australia
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	31,187		31,944
Rest of world
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	38,609		35,032
Stream interests
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	1,590,974		1,622,435
Revenue	86,981	70,037
Cost of sales	20,111	16,527
Depletion	31,462	32,097
Total segment gross profit	35,408	21,413
Stream interests | Canada
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	756,174		767,749
Revenue	37,663	14,747
Stream interests | Dominican Republic
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	441,443		451,585
Revenue	21,618	19,486
Stream interests | Chile
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	294,408		301,507
Revenue	20,604	27,742
Stream interests | Africa
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	86,910		89,555
Revenue	7,096	8,062
Stream interests | Rest of world
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	12,039		12,039
Royalty interests
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	714,044		716,881
Revenue	31,793	29,955
Production taxes	1,099	1,292
Depletion	7,199	10,408
Total segment gross profit	23,495	18,255
Royalty interests | Canada
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	197,409		200,251
Revenue	8,921	10,181
Royalty interests | Chile
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	214,225		214,226
Royalty interests | Africa
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	321		321
Revenue	470	492
Royalty interests | Mexico
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	81,920		83,748
Revenue	6,387	7,996
Royalty interests | United States
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	162,412		163,398
Revenue	10,602	6,056
Royalty interests | Australia
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	31,187		31,944
Revenue	3,802	3,060
Royalty interests | Rest of world
Long Lived Assets and Pre-Tax Income by Geographical Information
Stream and royalty interests, net	26,570		$ 22,993
Revenue	$ 1,611	$ 2,170