Guarantor Financial Statements (Unaudited) Condensed Consolidating Balance Sheets (Details) - USD ($) $ in Millions	Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Dec. 31, 2016
ASSETS
Current assets, other than assets held-for-sale	$ 10,921		$ 10,689
Property, plant, equipment and mine development costs, net	23,013		22,934
Investments in consolidated subsidiaries	0		0
Other assets	3,815		3,679
Total assets	37,749		37,302	$ 37,327
LIABILITIES AND EQUITY
Current liabilities, other than liabilities held for sale	3,851		5,011
Long-term debt, less current portion	11,123		11,703
Deferred income taxes	3,839		3,649
Environmental and asset retirement obligations, less current portion	3,564		3,631
Investments in consolidated subsidiaries	0		0
Other liabilities	1,918		2,012
Total liabilities	24,295		26,006
Equity:
Stockholders' equity	9,977		7,977
Noncontrolling interests	3,477		3,319
Total equity	13,454	$ 12,842	11,296	$ 10,230	$ 9,993	$ 9,257
Total liabilities and equity	37,749		37,302
Eliminations [Member]
ASSETS
Current assets, other than assets held-for-sale	(1,022)		(790)
Property, plant, equipment and mine development costs, net	0		(10)
Investments in consolidated subsidiaries	(19,681)		(19,570)
Other assets	(77)		(491)
Total assets	(20,780)		(20,861)
LIABILITIES AND EQUITY
Current liabilities, other than liabilities held for sale	(1,146)		(938)
Long-term debt, less current portion	(10,350)		(10,270)
Deferred income taxes	0		0
Environmental and asset retirement obligations, less current portion	0		0
Investments in consolidated subsidiaries	(11,025)		(11,250)
Other liabilities	(3,487)		(3,488)
Total liabilities	(26,008)		(25,946)
Equity:
Stockholders' equity	4,592		4,480
Noncontrolling interests	636		605
Total equity	5,228		5,085
Total liabilities and equity	(20,780)		(20,861)
FCX Issuer [Member] | Reportable Legal Entities [Member]
ASSETS
Current assets, other than assets held-for-sale	549		75
Property, plant, equipment and mine development costs, net	19		14
Investments in consolidated subsidiaries	19,681		19,570
Other assets	546		943
Total assets	20,795		20,602
LIABILITIES AND EQUITY
Current liabilities, other than liabilities held for sale	246		1,683
Long-term debt, less current portion	9,594		10,021
Deferred income taxes	820		748
Environmental and asset retirement obligations, less current portion	0		0
Investments in consolidated subsidiaries	0		0
Other liabilities	158		173
Total liabilities	10,818		12,625
Equity:
Stockholders' equity	9,977		7,977
Noncontrolling interests	0		0
Total equity	9,977		7,977
Total liabilities and equity	20,795		20,602
FM O&G LLC Guarantor [Member] | Reportable Legal Entities [Member]
ASSETS
Current assets, other than assets held-for-sale	577		671
Property, plant, equipment and mine development costs, net	3		11
Investments in consolidated subsidiaries	0		0
Other assets	67		48
Total assets	647		730
LIABILITIES AND EQUITY
Current liabilities, other than liabilities held for sale	137		220
Long-term debt, less current portion	6,784		6,512
Deferred income taxes	0		0
Environmental and asset retirement obligations, less current portion	209		201
Investments in consolidated subsidiaries	601		853
Other liabilities	3,340		3,340
Total liabilities	11,071		11,126
Equity:
Stockholders' equity	(10,424)		(10,396)
Noncontrolling interests	0		0
Total equity	(10,424)		(10,396)
Total liabilities and equity	647		730
Non-Guarantor Subsidiaries [Member] | Reportable Legal Entities [Member]
ASSETS
Current assets, other than assets held-for-sale	10,817		10,733
Property, plant, equipment and mine development costs, net	22,991		22,919
Investments in consolidated subsidiaries	0		0
Other assets	3,279		3,179
Total assets	37,087		36,831
LIABILITIES AND EQUITY
Current liabilities, other than liabilities held for sale	4,614		4,046
Long-term debt, less current portion	5,095		5,440
Deferred income taxes	3,019		2,901
Environmental and asset retirement obligations, less current portion	3,355		3,430
Investments in consolidated subsidiaries	10,424		10,397
Other liabilities	1,907		1,987
Total liabilities	28,414		28,201
Equity:
Stockholders' equity	5,832		5,916
Noncontrolling interests	2,841		2,714
Total equity	8,673		8,630
Total liabilities and equity	$ 37,087		$ 36,831