DISPOSITIONS AND ACQUISITIONS (Oil and Gas Operations) (Details) $ in Millions							1 Months Ended	3 Months Ended	12 Months Ended
	Jul. 31, 2017 USD ($)	Mar. 17, 2017 USD ($)	Dec. 30, 2016 USD ($)	Dec. 15, 2016 USD ($)	Jul. 25, 2016 USD ($)	Jun. 17, 2016 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2017 USD ($) $ / bbl	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Other current assets							$ 199.0	$ 199.0	$ 270.0	$ 199.0
Other assets							1,956.0	1,956.0	2,270.0	1,956.0
Net gain on sales of assets									(81.0)	(649.0)	$ (39.0)
Deepwater Gulf of Mexico and onshore California oil and gas properties
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from sales									0.0	2,272.0	$ 0.0
Freeport-McMoRan Oil & Gas
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net gain on sales of assets									(49.0)
Freeport-McMoRan Oil & Gas | Gulf of Mexico [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from sales	$ 62.0
Freeport-McMoRan Oil & Gas | Madden [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from sales		$ 17.5
Freeport-McMoRan Oil & Gas | Deepwater Gulf of Mexico and onshore California oil and gas properties
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net gain on sales of assets										9.0
Preferred stock redemption amount							582.0	582.0		582.0
Gain on redemption of preferred stock							199.0	199.0
Freeport-McMoRan Oil & Gas | Onshore California
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Contingent consideration asset			$ 150.0				33.0	33.0		33.0
Other assets							33.0	33.0	$ 34.0	33.0
Proceeds from sales			592.0
Freeport-McMoRan Oil & Gas | Onshore California | Crude Oil
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Contingent consideration, reference threshold, price per barrel (in us dollars per pound) | $ / bbl									70
Freeport-McMoRan Oil & Gas | Onshore California | Forecast
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Contingent consideration asset												$ 50.0	$ 50.0	$ 50.0
Freeport-McMoRan Oil & Gas | Deepwater Gulf of Mexico Interests
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Contingent consideration asset			$ 150.0				$ 150.0	$ 150.0		$ 150.0
Other current assets									$ 24.0
Other assets									$ 126.0
Proceeds from sales				$ 2,000.0
Freeport-McMoRan Oil & Gas | Haynesville
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from sales					$ 87.0
Freeport-McMoRan Oil & Gas | Black Stone Minerals, L.P.
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from sales						$ 102.0