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COMMITMENTS AND GUARANTEES (Special Mining License (IUPK)) (Details) T in Thousands, $ in Millions	3 Months Ended	12 Months Ended			13 Months Ended	21 Months Ended
	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Mar. 08, 2020 T	Dec. 21, 2018	Jan. 01, 2023
Contractual Obligations Mining Contracts [Line Items]
Smelter Development Progress, Higher Threshold, Percent		50.00%
Royalty Expense		$ 113	$ 246	$ 181
Export Duties Expense		221	180	115
Surety Bond
Contractual Obligations Mining Contracts [Line Items]
Assurance Bond, Smelter Development		$ 344
PT-FI
Contractual Obligations Mining Contracts [Line Items]
Progressive export duty on copper concentrates, lower threshold, percent		2.50%
Progressive export duty on copper concentrates, higher threshold, percent		5.00%				7.50%
Smelter Development Progress, Lower Threshold, Percent		30.00%
Royalty Expense		$ 106	238	173
Export Duties Expense		$ 66	$ 180	$ 115
PT-FI \| Copper
Contractual Obligations Mining Contracts [Line Items]
Royalty Interest in Future Production		4.00%
PT-FI \| Gold
Contractual Obligations Mining Contracts [Line Items]
Royalty Interest in Future Production		3.75%
PT-FI \| Silver
Contractual Obligations Mining Contracts [Line Items]
Royalty Interest in Future Production		3.25%
PT-FI \| Construction Contracts \| Surety Bond
Contractual Obligations Mining Contracts [Line Items]
Assurance Bond, Smelter Development		$ 157
PT-FI
Contractual Obligations Mining Contracts [Line Items]
Ownership percentage		48.76%				81.28%
PT-FI \| PT Indocopper Investama [Member]
Contractual Obligations Mining Contracts [Line Items]
Ownership percentage						9.36%
Tax Authority, In Papua, Indonesia
Contractual Obligations Mining Contracts [Line Items]
Foreign income tax rate under new stability agreement		25.00%
Foreign Profits Tax Rate on Net Income Under New Stability Agreement		10.00%
Forecast [Member]
Contractual Obligations Mining Contracts [Line Items]
Copper Concentrate, Export Quota, Original \| T					180
Copper Concentrate, Export Quota, Revised \| T					680
Forecast [Member] \| PT-FI
Contractual Obligations Mining Contracts [Line Items]
Ownership percentage							48.76%
Memorandum of Understanding with the Indonesian Government, Indonesia Supreme Court Appeal [Member] \| Indonesia Tax Authority \| PT-FI
Contractual Obligations Mining Contracts [Line Items]
Progressive export duty on copper concentrates, lower threshold, percent		5.00%
Loss Contingency, Loss in Period	$ 155	$ 155
Annual Surface Water Tax Payments [Member] \| PT-FI
Contractual Obligations Mining Contracts [Line Items]
Payments for Other Taxes		$ 15