STREAM AND ROYALTY INTERESTS, NET - Impairments (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Mar. 31, 2018	Mar. 31, 2018
Impairments of royalty interests	$ 239,364	$ 239,364
Pascua-Lama
Impairments of royalty interests	239,080	$ 239,080
Copper NSR (as a percent)		1.09%
Other
Impairments of royalty interests	$ 284	$ 284
Minimum \| Pascua-Lama
Net smelter return (NSR) (as a percent)		0.78%
Maximum \| Pascua-Lama
Net smelter return (NSR) (as a percent)		5.45%

Amount of write-down of assets recognized in the income statement. Includes, but is not limited to, losses from tangible assets, intangible assets and goodwill.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 45
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=68055307&loc=d3e2420-110228

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3602-108585

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration