SEGMENT INFORMATION (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Mar. 31, 2018 USD ($)	Mar. 31, 2017 USD ($)	Mar. 31, 2018 USD ($) segment	Mar. 31, 2017 USD ($)	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	$ 2,532,603		$ 2,532,603		$ 2,892,256
Impairments	(239,364)		(239,364)
Revenue	115,983	$ 106,972	342,807	$ 331,880
Cost of sales	21,345	22,419	61,627	67,582
Net revenue	94,638	84,553	281,180	264,298
Canada
Long Lived Assets and Pre-Tax Income by Geographical Information
Value of stream and royalty interests, net	1,037,591		1,037,591		1,073,653
Impairments	(284)		(284)
Dominican Republic
Long Lived Assets and Pre-Tax Income by Geographical Information
Value of stream and royalty interests, net	509,211		509,211		543,256
Chile
Long Lived Assets and Pre-Tax Income by Geographical Information
Value of stream and royalty interests, net	548,492		548,492		802,147
Impairments	(239,080)		(239,080)
Africa
Long Lived Assets and Pre-Tax Income by Geographical Information
Value of stream and royalty interests, net	107,607		107,607		124,332
Mexico
Long Lived Assets and Pre-Tax Income by Geographical Information
Value of stream and royalty interests, net	95,234		95,234		105,889
United States
Long Lived Assets and Pre-Tax Income by Geographical Information
Value of stream and royalty interests, net	167,253		167,253		168,378
Australia
Long Lived Assets and Pre-Tax Income by Geographical Information
Value of stream and royalty interests, net	35,088		35,088		37,409
Other
Long Lived Assets and Pre-Tax Income by Geographical Information
Value of stream and royalty interests, net	32,127		32,127		37,192
Stream interest
Long Lived Assets and Pre-Tax Income by Geographical Information
Value of stream and royalty interests, net	1,783,245		1,783,245		1,879,859
Revenue	82,979	76,597	241,028	236,108
Cost of sales	21,345	22,419	61,627	67,582
Net revenue	61,634	54,178	179,401	168,526
Stream interest | Canada
Long Lived Assets and Pre-Tax Income by Geographical Information
Value of stream and royalty interests, net	820,639		820,639		852,035
Revenue	51,709	35,112	106,363	105,161
Cost of sales	14,225	12,583	30,072	36,341
Net revenue	37,484	22,529	76,291	68,820
Stream interest | Dominican Republic
Long Lived Assets and Pre-Tax Income by Geographical Information
Value of stream and royalty interests, net	509,211		509,211		543,256
Revenue	15,734	24,524	67,492	71,911
Cost of sales	4,415	7,054	20,200	21,497
Net revenue	11,319	17,470	47,292	50,414
Stream interest | Chile
Long Lived Assets and Pre-Tax Income by Geographical Information
Value of stream and royalty interests, net	334,266		334,266		348,778
Revenue	7,186	10,398	41,124	41,552
Cost of sales	1,039	1,499	6,148	6,243
Net revenue	6,147	8,899	34,976	35,309
Stream interest | Africa
Long Lived Assets and Pre-Tax Income by Geographical Information
Value of stream and royalty interests, net	107,092		107,092		123,760
Revenue	8,350	6,563	26,049	17,484
Cost of sales	1,666	1,283	5,207	3,501
Net revenue	6,684	5,280	20,842	13,983
Stream interest | Other
Long Lived Assets and Pre-Tax Income by Geographical Information
Value of stream and royalty interests, net	12,037		12,037		12,030
Royalty interest
Long Lived Assets and Pre-Tax Income by Geographical Information
Value of stream and royalty interests, net	988,722		988,722		1,012,397
Revenue	33,004	30,375	101,779	95,772
Net revenue	33,004	30,375	101,779	95,772
Royalty interest | Canada
Long Lived Assets and Pre-Tax Income by Geographical Information
Value of stream and royalty interests, net	217,236		217,236		221,618
Revenue	6,089	5,535	17,577	17,405
Net revenue	6,089	5,535	17,577	17,405
Royalty interest | Chile
Long Lived Assets and Pre-Tax Income by Geographical Information
Value of stream and royalty interests, net	453,306		453,306		453,369
Revenue			399	1,333
Net revenue			399	1,333
Royalty interest | Africa
Long Lived Assets and Pre-Tax Income by Geographical Information
Value of stream and royalty interests, net	515		515		572
Revenue	543	672	1,589	2,260
Net revenue	543	672	1,589	2,260
Royalty interest | Mexico
Long Lived Assets and Pre-Tax Income by Geographical Information
Value of stream and royalty interests, net	95,234		95,234		105,889
Revenue	11,021	10,446	32,772	31,573
Net revenue	11,021	10,446	32,772	31,573
Royalty interest | United States
Long Lived Assets and Pre-Tax Income by Geographical Information
Value of stream and royalty interests, net	167,253		167,253		168,378
Revenue	8,459	7,899	31,186	27,012
Net revenue	8,459	7,899	31,186	27,012
Royalty interest | Australia
Long Lived Assets and Pre-Tax Income by Geographical Information
Value of stream and royalty interests, net	35,088		35,088		37,409
Revenue	3,343	3,174	9,891	9,867
Net revenue	3,343	3,174	9,891	9,867
Royalty interest | Other
Long Lived Assets and Pre-Tax Income by Geographical Information
Value of stream and royalty interests, net	20,090		20,090		$ 25,162
Revenue	3,549	2,649	8,365	6,322
Net revenue	$ 3,549	$ 2,649	$ 8,365	$ 6,322