SEGMENT INFORMATION (Details) $ in Thousands	3 Months Ended
	Sep. 30, 2017 USD ($) segment	Sep. 30, 2016 USD ($)	Jun. 30, 2017 USD ($)
Long Lived Assets and Pre-Tax Income by Geographical Information
Number of reportable segments | segment	2
Value of stream and royalty interests, net	$ 2,852,598		$ 2,892,256
Revenue	112,476	$ 117,947
Cost of sales	20,419	22,662
Net revenue	92,057	95,285
Canada
Long Lived Assets and Pre-Tax Income by Geographical Information
Value of stream and royalty interests, net	1,063,095		1,073,653
Dominican Republic
Long Lived Assets and Pre-Tax Income by Geographical Information
Value of stream and royalty interests, net	530,603		543,256
Chile
Long Lived Assets and Pre-Tax Income by Geographical Information
Value of stream and royalty interests, net	797,829		802,147
Africa
Long Lived Assets and Pre-Tax Income by Geographical Information
Value of stream and royalty interests, net	118,333		124,332
Mexico
Long Lived Assets and Pre-Tax Income by Geographical Information
Value of stream and royalty interests, net	103,039		105,889
United States
Long Lived Assets and Pre-Tax Income by Geographical Information
Value of stream and royalty interests, net	167,430		168,378
Australia
Long Lived Assets and Pre-Tax Income by Geographical Information
Value of stream and royalty interests, net	36,563		37,409
Other
Long Lived Assets and Pre-Tax Income by Geographical Information
Value of stream and royalty interests, net	35,706		37,192
Stream interest
Long Lived Assets and Pre-Tax Income by Geographical Information
Value of stream and royalty interests, net	1,847,809		1,879,859
Revenue	78,762	85,504
Cost of sales	20,419	22,662
Net revenue	58,343	62,842
Stream interest | Canada
Long Lived Assets and Pre-Tax Income by Geographical Information
Value of stream and royalty interests, net	842,935		852,035
Revenue	31,952	38,386
Cost of sales	9,223	12,578
Net revenue	22,729	25,808
Stream interest | Dominican Republic
Long Lived Assets and Pre-Tax Income by Geographical Information
Value of stream and royalty interests, net	530,603		543,256
Revenue	25,403	20,950
Cost of sales	7,588	5,896
Net revenue	17,815	15,054
Stream interest | Chile
Long Lived Assets and Pre-Tax Income by Geographical Information
Value of stream and royalty interests, net	344,460		348,778
Revenue	12,337	20,169
Cost of sales	1,812	2,998
Net revenue	10,525	17,171
Stream interest | Africa
Long Lived Assets and Pre-Tax Income by Geographical Information
Value of stream and royalty interests, net	117,780		123,760
Revenue	9,070	5,999
Cost of sales	1,796	1,190
Net revenue	7,274	4,809
Stream interest | Other
Long Lived Assets and Pre-Tax Income by Geographical Information
Value of stream and royalty interests, net	12,031		12,030
Royalty interest
Long Lived Assets and Pre-Tax Income by Geographical Information
Value of stream and royalty interests, net	1,004,789		1,012,397
Revenue	33,714	32,443
Net revenue	33,714	32,443
Royalty interest | Canada
Long Lived Assets and Pre-Tax Income by Geographical Information
Value of stream and royalty interests, net	220,160		221,618
Revenue	6,092	6,188
Net revenue	6,092	6,188
Royalty interest | Chile
Long Lived Assets and Pre-Tax Income by Geographical Information
Value of stream and royalty interests, net	453,369		453,369
Revenue		489
Net revenue		489
Royalty interest | Africa
Long Lived Assets and Pre-Tax Income by Geographical Information
Value of stream and royalty interests, net	553		572
Revenue	462	824
Net revenue	462	824
Royalty interest | Mexico
Long Lived Assets and Pre-Tax Income by Geographical Information
Value of stream and royalty interests, net	103,039		105,889
Revenue	10,897	9,596
Net revenue	10,897	9,596
Royalty interest | United States
Long Lived Assets and Pre-Tax Income by Geographical Information
Value of stream and royalty interests, net	167,430		168,378
Revenue	10,429	9,706
Net revenue	10,429	9,706
Royalty interest | Australia
Long Lived Assets and Pre-Tax Income by Geographical Information
Value of stream and royalty interests, net	36,563		37,409
Revenue	3,320	3,462
Net revenue	3,320	3,462
Royalty interest | Other
Long Lived Assets and Pre-Tax Income by Geographical Information
Value of stream and royalty interests, net	23,675		$ 25,162
Revenue	2,514	2,178
Net revenue	$ 2,514	$ 2,178