GUARANTOR FINANCIAL STATEMENTS (Condensed Consolidating Comprehensive (Loss) Income) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Condensed Comprehensive (Loss) Income Statements [Line Items]
Revenues	$ 3,684	$ 4,908	$ 5,168	$ 4,868	$ 5,041	$ 4,310	$ 3,711	$ 3,341	$ 18,628	$ 16,403	$ 14,830
Costs and Expenses									13,874	12,713	17,559
Operating income (loss)	316	1,315	1,664	1,459	1,479	928	686	597	4,754	3,690	(2,729)
Interest expense, net									(945)	(801)	(755)
Other income (expense), net									76	(8)	(14)
Net gain on early extinguishment and exchanges of debt									7	21	26
Other Operating Income (Expense) Including Gain (Loss) on Early Extinguishment of Debt									76	(8)
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest									3,892	2,902	(3,472)
Benefit from (provision for) income taxes									(991)	(883)	(371)
Equity in affiliated companies’ net earnings (losses)									8	10	11
Net income (loss) from continuing operations	374	668	1,039	828	1,193	242	326	268	2,909	2,029	(3,832)
Net (loss) income from discontinued operations	4	(4)	(4)	(11)	16	3	9	38	(15)	66	(193)
Net income (loss)	378	664	1,035	817	1,209	245	335	306	2,894	2,095	(4,025)
Net income from continuing operations attributable to noncontrolling interests											(66)
Net income (loss) attributable to noncontrolling interests: Discontinued Operations					0	0	1	3	0	4	63
Net (loss) income attributable to common stockholders	$ 485	$ 556	$ 869	$ 692	$ 1,041	$ 280	$ 268	$ 228	2,602	1,817	(4,154)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent									(33)	61	(45)
Total comprehensive income (loss) attributable to common stockholders									2,569	1,878	(4,199)
Eliminations
Condensed Comprehensive (Loss) Income Statements [Line Items]
Revenues									0	0	0
Costs and Expenses									(10)	10	10
Operating income (loss)									10	(10)	(10)
Interest expense, net									478	348	333
Other income (expense), net											(292)
Net gain on early extinguishment and exchanges of debt									0	0	0
Other Operating Income (Expense) Including Gain (Loss) on Early Extinguishment of Debt									(478)	(348)
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest									10	(10)	31
Benefit from (provision for) income taxes									(2)	3	(12)
Equity in affiliated companies’ net earnings (losses)									(2,493)	(1,408)	9,511
Net income (loss) from continuing operations									(2,485)	(1,415)	9,530
Net (loss) income from discontinued operations									0	0	(39)
Net income (loss)									(2,485)	(1,415)	9,491
Net income from continuing operations attributable to noncontrolling interests											(66)
Net income (loss) attributable to noncontrolling interests: Discontinued Operations										0	0
Net (loss) income attributable to common stockholders									(2,709)	(1,539)	9,425
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent									33	(61)	45
Total comprehensive income (loss) attributable to common stockholders									(2,676)	(1,600)	9,470
FCX Issuer
Condensed Comprehensive (Loss) Income Statements [Line Items]
Net gain on early extinguishment and exchanges of debt										22
FCX Issuer | Reportable Legal Entities
Condensed Comprehensive (Loss) Income Statements [Line Items]
Revenues									0	0	0
Costs and Expenses									28	39	72
Operating income (loss)									(28)	(39)	(72)
Interest expense, net									(388)	(467)	(534)
Other income (expense), net											268
Net gain on early extinguishment and exchanges of debt									7		26
Other Operating Income (Expense) Including Gain (Loss) on Early Extinguishment of Debt									477	336
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest									68	(148)	(312)
Benefit from (provision for) income taxes									(176)	220	(2,233)
Equity in affiliated companies’ net earnings (losses)									2,710	1,745	(1,609)
Net income (loss) from continuing operations									2,602	1,817	(4,154)
Net (loss) income from discontinued operations									0	0	0
Net income (loss)									2,602	1,817	(4,154)
Net income from continuing operations attributable to noncontrolling interests											0
Net income (loss) attributable to noncontrolling interests: Discontinued Operations										0	0
Net (loss) income attributable to common stockholders									2,602	1,817	(4,154)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent									(33)	61	(45)
Total comprehensive income (loss) attributable to common stockholders									2,569	1,878	(4,199)
FM O&G LLC Guarantor
Condensed Comprehensive (Loss) Income Statements [Line Items]
Impairment of oil and gas properties											1,500
FM O&G LLC Guarantor | Reportable Legal Entities
Condensed Comprehensive (Loss) Income Statements [Line Items]
Revenues									59	52	379
Costs and Expenses									58	78	3,074
Operating income (loss)									1	(26)	(2,695)
Interest expense, net									(301)	(227)	(56)
Other income (expense), net											0
Net gain on early extinguishment and exchanges of debt									2	5	0
Other Operating Income (Expense) Including Gain (Loss) on Early Extinguishment of Debt									0	0
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest									(298)	(248)	(2,751)
Benefit from (provision for) income taxes									61	(108)	1,053
Equity in affiliated companies’ net earnings (losses)									10	10	(3,101)
Net income (loss) from continuing operations									(227)	(346)	(4,799)
Net (loss) income from discontinued operations									0	0	0
Net income (loss)									(227)	(346)	(4,799)
Net income from continuing operations attributable to noncontrolling interests											0
Net income (loss) attributable to noncontrolling interests: Discontinued Operations										0	0
Net (loss) income attributable to common stockholders									(227)	(346)	(4,799)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent									0	0	0
Total comprehensive income (loss) attributable to common stockholders									(227)	(346)	(4,799)
Non-Guarantor Subsidiaries
Condensed Comprehensive (Loss) Income Statements [Line Items]
Impairment of oil and gas properties											2,800
Non-Guarantor Subsidiaries | Reportable Legal Entities
Condensed Comprehensive (Loss) Income Statements [Line Items]
Revenues									18,569	16,351	14,451
Costs and Expenses									13,798	12,586	14,403
Operating income (loss)									4,771	3,765	48
Interest expense, net									(734)	(455)	(498)
Other income (expense), net											10
Net gain on early extinguishment and exchanges of debt									(2)	(6)	0
Other Operating Income (Expense) Including Gain (Loss) on Early Extinguishment of Debt									77	4
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest									4,112	3,308	(440)
Benefit from (provision for) income taxes									(874)	(998)	821
Equity in affiliated companies’ net earnings (losses)									(219)	(337)	(4,790)
Net income (loss) from continuing operations									3,019	1,973	(4,409)
Net (loss) income from discontinued operations									(15)	66	(154)
Net income (loss)									3,004	2,039	(4,563)
Net income from continuing operations attributable to noncontrolling interests											0
Net income (loss) attributable to noncontrolling interests: Discontinued Operations										4	63
Net (loss) income attributable to common stockholders									2,936	1,885	(4,626)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent									(33)	61	(45)
Total comprehensive income (loss) attributable to common stockholders									$ 2,903	$ 1,946	$ (4,671)