STREAM AND ROYALTY INTERESTS, NET - Summary (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Jun. 30, 2018
Cost	$ 3,396,946	$ 3,636,306
Accumulated Depletion	(938,331)	(895,825)
Impairments		(239,364)
Net	2,458,615	2,501,117
Total production stage stream and royalty interests
Cost	2,955,604	2,955,604
Accumulated Depletion	(938,331)	(895,825)
Net	2,017,273	2,059,779
Production stage stream interests
Cost	2,111,423	2,111,423
Accumulated Depletion	(405,353)	(373,257)
Net	1,706,070	1,738,166
Production stage stream interests | Mount Milligan
Cost	790,635	790,635
Accumulated Depletion	(155,695)	(152,833)
Net	634,940	637,802
Production stage stream interests | Pueblo Viejo
Cost	610,404	610,404
Accumulated Depletion	(125,261)	(114,944)
Net	485,143	495,460
Production stage stream interests | Andacollo
Cost	388,182	388,182
Accumulated Depletion	(70,747)	(59,851)
Net	317,435	328,331
Production stage stream interests | Wassa and Prestea
Cost	146,475	146,475
Accumulated Depletion	(46,711)	(41,601)
Net	99,764	104,874
Production stage stream interests | Rainy River
Cost	175,727	175,727
Accumulated Depletion	(6,939)	(4,028)
Net	168,788	171,699
Production stage royalty interests
Cost	844,181	844,181
Accumulated Depletion	(532,978)	(522,568)
Net	311,203	321,613
Production stage royalty interests | Voisey's Bay
Cost	205,724	205,724
Accumulated Depletion	(90,006)	(86,933)
Net	115,718	118,791
Production stage royalty interests | Penasquito
Cost	99,172	99,172
Accumulated Depletion	(39,054)	(38,426)
Net	60,118	60,746
Production stage royalty interests | Holt
Cost	34,612	34,612
Accumulated Depletion	(21,569)	(21,173)
Net	13,043	13,439
Production stage royalty interests | Cortez
Cost	20,878	20,878
Accumulated Depletion	(11,275)	(11,241)
Net	9,603	9,637
Production stage royalty interests | Other
Cost	483,795	483,795
Accumulated Depletion	(371,074)	(364,795)
Net	112,721	119,000
Total development stage stream and royalty interests
Cost	146,170	146,451
Impairments		(284)
Net	146,170	146,167
Development stage stream interests | Other
Cost	12,038	12,038
Net	12,038	12,038
Development stage royalty interests
Cost	134,132	134,413
Impairments		(284)
Net	134,132	134,129
Development stage royalty interests | Cortez
Cost	59,803	59,803
Net	59,803	59,803
Development stage royalty interests | Other
Cost	74,329	74,610
Impairments		(284)
Net	74,329	74,326
Exploration stage royalty interests
Cost	295,172	534,251
Impairments		(239,080)
Net	295,172	295,171
Exploration stage royalty interests | Pascua-Lama
Cost	177,690	416,770
Impairments		(239,080)
Net	177,690	177,690
Exploration stage royalty interests | Other
Cost	117,482	117,481
Net	$ 117,482	$ 117,481