Fair Value Measurement (Fair Value Measurement Inputs) (Details) $ in Millions	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Dec. 31, 2016 USD ($) $ / bbl	Nov. 16, 2016 USD ($) $ / lb
Fair Value, Assets and Liabilities Measured on Recurring Basis, Financial Statement Captions [Line Items]
Other current assets				$ 402	$ 270
Other assets				2,460	2,270
Assets				37,749	37,302	$ 37,327
Derivative Liability, Fair Value, Gross Liability				59	33
Derivatives:
Derivative Asset				37	166
Derivatives: [Abstract]
Derivative Liability				42	32
Fair Value Measured at Net Asset Value Per Share [Member]
Investment securities (current and long-term):
Investments, Fair Value Disclosure				24	25
Trust Assets Fair Value Disclosure				54	55
Level 1
Investment securities (current and long-term):
Investments, Fair Value Disclosure				5	5
Trust Assets Fair Value Disclosure				3	11
Derivatives:
Derivative Asset				4	9
Contingent receivable				0	0
Derivatives: [Abstract]
Derivative Liability				4	1
Long-term debt, including current portion				0	0
Level 2
Investment securities (current and long-term):
Investments, Fair Value Disclosure				0	0
Trust Assets Fair Value Disclosure				121	123
Derivatives:
Derivative Asset				217	266
Contingent receivable				0	0
Derivatives: [Abstract]
Derivative Liability				51	32
Long-term debt, including current portion				10,865	13,269
Level 3
Investment securities (current and long-term):
Investments, Fair Value Disclosure				0	0
Trust Assets Fair Value Disclosure				0	0
Derivatives:
Derivative Asset				0	0
Contingent receivable				130	134
Derivatives: [Abstract]
Derivative Liability				0	0
Long-term debt, including current portion				0	0
Estimate of Fair Value Measurement [Member]
Investment securities (current and long-term):
Investments, Fair Value Disclosure				29	30
Trust Assets Fair Value Disclosure				178	189
Derivatives:
Derivative Asset				221	275
Contingent receivable				130	134
Derivatives: [Abstract]
Derivative Liability				55	33
Long-term debt, including current portion				10,865	13,269
Carrying Amount, Fair Value Disclosure [Member]
Investment securities (current and long-term):
Investments, Fair Value Disclosure				29	30
Trust Assets Fair Value Disclosure				178	189
Derivatives:
Derivative Asset				221	275
Contingent receivable				148	150
Derivatives: [Abstract]
Derivative Liability				55	33
Long-term debt, including current portion				11,127	13,117
Embedded Derivative Financial Instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis, Financial Statement Captions [Line Items]
Derivative Liability, Fair Value, Gross Liability				50	31
Derivatives:
Derivative Asset				37	155
Derivatives: [Abstract]
Derivative Liability				38	31
Embedded Derivative Financial Instruments [Member] | Level 1
Derivatives:
Derivative Asset				0	0
Derivatives: [Abstract]
Derivative Liability				0	0
Embedded Derivative Financial Instruments [Member] | Level 2
Derivatives:
Derivative Asset				49	155
Derivatives: [Abstract]
Derivative Liability				50	31
Embedded Derivative Financial Instruments [Member] | Level 3
Derivatives:
Derivative Asset				0	0
Derivatives: [Abstract]
Derivative Liability				0	0
Embedded Derivative Financial Instruments [Member] | Estimate of Fair Value Measurement [Member]
Derivatives:
Derivative Asset				49	155
Derivatives: [Abstract]
Derivative Liability				50	31
Embedded Derivative Financial Instruments [Member] | Carrying Amount, Fair Value Disclosure [Member]
Derivatives:
Derivative Asset				49	155
Derivatives: [Abstract]
Derivative Liability				50	31
Forward Contracts [Member] | Level 1
Derivatives:
Derivative Asset					0
Forward Contracts [Member] | Level 2
Derivatives:
Derivative Asset					1
Forward Contracts [Member] | Level 3
Derivatives:
Derivative Asset					0
Forward Contracts [Member] | Estimate of Fair Value Measurement [Member]
Derivatives:
Derivative Asset					1
Forward Contracts [Member] | Carrying Amount, Fair Value Disclosure [Member]
Derivatives:
Derivative Asset					1
Commodity Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis, Financial Statement Captions [Line Items]
Derivative Liability, Fair Value, Gross Liability				9	2
Derivatives:
Derivative Asset				0	11
Derivatives: [Abstract]
Derivative Liability				4	1
Commodity Contract [Member] | Level 1
Derivatives:
Derivative Asset					9
Derivatives: [Abstract]
Derivative Liability				4
Commodity Contract [Member] | Level 2
Derivatives:
Derivative Asset					2
Derivatives: [Abstract]
Derivative Liability				1
Commodity Contract [Member] | Level 3
Derivatives:
Derivative Asset					0
Derivatives: [Abstract]
Derivative Liability				0
Commodity Contract [Member] | Estimate of Fair Value Measurement [Member]
Derivatives:
Derivative Asset					11
Derivatives: [Abstract]
Derivative Liability				5
Commodity Contract [Member] | Carrying Amount, Fair Value Disclosure [Member]
Derivatives:
Derivative Asset					11
Derivatives: [Abstract]
Derivative Liability				5
Future [Member] | Level 1
Derivatives:
Derivative Asset				4
Future [Member] | Level 2
Derivatives:
Derivative Asset				1
Future [Member] | Level 3
Derivatives:
Derivative Asset				0
Future [Member] | Estimate of Fair Value Measurement [Member]
Derivatives:
Derivative Asset				5
Future [Member] | Carrying Amount, Fair Value Disclosure [Member]
Derivatives:
Derivative Asset				5
Africa and onshore California [Member] | Commodity Contract [Member] | Level 1
Derivatives:
Derivative Asset				0	0
Africa and onshore California [Member] | Commodity Contract [Member] | Level 2
Derivatives:
Derivative Asset				167	108
Africa and onshore California [Member] | Commodity Contract [Member] | Level 3
Derivatives:
Derivative Asset				0	0
Africa and onshore California [Member] | Commodity Contract [Member] | Estimate of Fair Value Measurement [Member]
Derivatives:
Derivative Asset				167	108
Africa and onshore California [Member] | Commodity Contract [Member] | Carrying Amount, Fair Value Disclosure [Member]
Derivatives:
Derivative Asset				167	108
U.S. core fixed income fund [Member] | Fair Value Measured at Net Asset Value Per Share [Member]
Investment securities (current and long-term):
Marketable Securities				24	25
Trust Assets Fair Value Disclosure				54	55
U.S. core fixed income fund [Member] | Level 1
Investment securities (current and long-term):
Marketable Securities				0	0
Trust Assets Fair Value Disclosure				0	0
U.S. core fixed income fund [Member] | Level 2
Investment securities (current and long-term):
Marketable Securities				0	0
Trust Assets Fair Value Disclosure				0	0
U.S. core fixed income fund [Member] | Level 3
Investment securities (current and long-term):
Marketable Securities				0	0
Trust Assets Fair Value Disclosure				0	0
U.S. core fixed income fund [Member] | Estimate of Fair Value Measurement [Member]
Investment securities (current and long-term):
Marketable Securities				24	25
Trust Assets Fair Value Disclosure				54	55
U.S. core fixed income fund [Member] | Carrying Amount, Fair Value Disclosure [Member]
Investment securities (current and long-term):
Marketable Securities				24	25
Trust Assets Fair Value Disclosure				54	55
Equity securities | Level 1
Investment securities (current and long-term):
Marketable Securities				5	5
Equity securities | Level 2
Investment securities (current and long-term):
Marketable Securities				0	0
Equity securities | Level 3
Investment securities (current and long-term):
Marketable Securities				0	0
Equity securities | Estimate of Fair Value Measurement [Member]
Investment securities (current and long-term):
Marketable Securities				5	5
Equity securities | Carrying Amount, Fair Value Disclosure [Member]
Investment securities (current and long-term):
Marketable Securities				5	5
Government bonds | Level 1
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure				0	0
Government bonds | Level 2
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure				31	40
Government bonds | Level 3
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure				0	0
Government bonds | Estimate of Fair Value Measurement [Member]
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure				31	40
Government bonds | Carrying Amount, Fair Value Disclosure [Member]
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure				31	40
Corporate bonds [Member] | Level 1
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure				0	0
Corporate bonds [Member] | Level 2
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure				28	32
Corporate bonds [Member] | Level 3
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure				0	0
Corporate bonds [Member] | Estimate of Fair Value Measurement [Member]
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure				28	32
Corporate bonds [Member] | Carrying Amount, Fair Value Disclosure [Member]
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure				28	32
Government mortgage-backed securities [Member] | Level 1
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure				0	0
Government mortgage-backed securities [Member] | Level 2
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure				39	27
Government mortgage-backed securities [Member] | Level 3
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure				0	0
Government mortgage-backed securities [Member] | Estimate of Fair Value Measurement [Member]
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure				39	27
Government mortgage-backed securities [Member] | Carrying Amount, Fair Value Disclosure [Member]
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure				39	27
Asset-backed securities [Member] | Level 1
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure				0	0
Asset-backed securities [Member] | Level 2
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure				14	15
Asset-backed securities [Member] | Level 3
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure				0	0
Asset-backed securities [Member] | Estimate of Fair Value Measurement [Member]
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure				14	15
Asset-backed securities [Member] | Carrying Amount, Fair Value Disclosure [Member]
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure				14	15
Money market funds [Member] | Level 1
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure				3	11
Money market funds [Member] | Level 2
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure				0	0
Money market funds [Member] | Level 3
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure				0	0
Money market funds [Member] | Estimate of Fair Value Measurement [Member]
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure				3	11
Money market funds [Member] | Carrying Amount, Fair Value Disclosure [Member]
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure				3	11
Collateralized Mortgage Backed Securities [Member] | Level 1
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure				0	0
Collateralized Mortgage Backed Securities [Member] | Level 2
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure				8	8
Collateralized Mortgage Backed Securities [Member] | Level 3
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure				0	0
Collateralized Mortgage Backed Securities [Member] | Estimate of Fair Value Measurement [Member]
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure				8	8
Collateralized Mortgage Backed Securities [Member] | Carrying Amount, Fair Value Disclosure [Member]
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure				8	8
Municipal bonds [Member] | Level 1
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure				0	0
Municipal bonds [Member] | Level 2
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure				1	1
Municipal bonds [Member] | Level 3
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure				0	0
Municipal bonds [Member] | Estimate of Fair Value Measurement [Member]
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure				1	1
Municipal bonds [Member] | Carrying Amount, Fair Value Disclosure [Member]
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure				1	1
Bank Time Deposits [Member] | Carrying Amount, Fair Value Disclosure [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis, Financial Statement Captions [Line Items]
Other current assets				116	52
Other assets				126	123
Commodity Contract [Member] | Level 1
Derivatives: [Abstract]
Derivative Liability					1
Commodity Contract [Member] | Level 2
Derivatives: [Abstract]
Derivative Liability					1
Commodity Contract [Member] | Level 3
Derivatives: [Abstract]
Derivative Liability					0
Commodity Contract [Member] | Estimate of Fair Value Measurement [Member]
Derivatives: [Abstract]
Derivative Liability					2
Commodity Contract [Member] | Carrying Amount, Fair Value Disclosure [Member]
Derivatives: [Abstract]
Derivative Liability					2
Not Designated as Hedging Instrument [Member] | Embedded Derivative Financial Instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis, Financial Statement Captions [Line Items]
Derivative Liability, Fair Value, Gross Liability				50	31
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Estimate of Fair Value Measurement [Member]
Derivatives: [Abstract]
Long-term debt, including current portion				160	112
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Not Designated as Hedging Instrument [Member] | Embedded Derivative Financial Instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis, Financial Statement Captions [Line Items]
Derivative Liability, Fair Value, Gross Liability				12	24
TF Holdings Limited | Discontinued Operations, Disposed of by Sale
Fair Value, Assets and Liabilities Measured on Recurring Basis, Financial Statement Captions [Line Items]
Other assets				57	74
Derivatives:
Contingent receivable								$ 120
Copper | TF Holdings Limited | Discontinued Operations, Disposed of by Sale
Derivatives:
Contingent receivable								60
Cobalt | Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | Not Designated as Hedging Instrument [Member] | Embedded Derivative Financial Instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis, Financial Statement Captions [Line Items]
Derivative Liability, Fair Value, Gross Liability				12	24
Cobalt | TF Holdings Limited | Discontinued Operations, Disposed of by Sale
Derivatives:
Contingent receivable								$ 60
Contingent consideration, reference threshold (in us dollars per pound) | $ / lb								20
Freeport-McMoRan Oil & Gas | Onshore California [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis, Financial Statement Captions [Line Items]
Other current assets				49
Other assets					34
Assets				110
Derivatives:
Contingent receivable							$ 150
Freeport-McMoRan Oil & Gas | Deepwater Gulf of Mexico Interests [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis, Financial Statement Captions [Line Items]
Other current assets				12	24
Other assets				$ 136	$ 126
Derivatives:
Contingent receivable							$ 150
Scenario, Forecast [Member] | Freeport-McMoRan Oil & Gas | Onshore California [Member]
Derivatives:
Contingent receivable	$ 50	$ 50	$ 50
Crude Oil [Member] | Freeport-McMoRan Oil & Gas | Onshore California [Member]
Derivatives:
Contingent consideration, reference threshold (in us dollars per pound) | $ / bbl							70
Maximum [Member] | Copper | TF Holdings Limited | Discontinued Operations, Disposed of by Sale
Derivatives:
Contingent consideration, reference threshold (in us dollars per pound) | $ / lb								3.50