BASIS OF PRESENTATION - Stock issuance and mine acquisition (Details) - USD ($) $ in Millions		9 Months Ended
Aug. 03, 2015	Sep. 30, 2015
Common stock issuance
Net proceeds from common stock issuance		$ 675
Cripple Creek & Victor mine
Business combination, terms
Acquisition price	$ 821
Cripple Creek & Victor mine \| Smelter Return Royalty
Business combination, terms
Net smelter return royalty (as a percent)	2.50%

The cash outflow associated with the acquisition of business during the period. The cash portion only of the acquisition price.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Investing Activities

-URI http://asc.fasb.org/extlink&oid=6516133

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 13

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3213-108585

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