SUMMARY OF POLICIES - Income and Mining Taxes (Details) $ in Millions	12 Months Ended
Dec. 31, 2019 USD ($)
Income and Mining Taxes
Deferred tax on unremitted earnings	$ 0
Look-back period	3 years

Amount of deferred tax liability attributable to taxable temporary differences from undistributed earnings of subsidiary and other recognized entity not within country of domicile. Includes, but is not limited to, other basis differences.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32621-109319

Name:	us-gaap_DeferredTaxLiabilitiesUndistributedForeignEarnings
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant