Fair Value Measurement (Fair Value Measurement Inputs) (Details) $ in Millions	9 Months Ended		12 Months Ended
	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($) $ / bbl	Dec. 31, 2016 USD ($) $ / bbl	Nov. 30, 2016 USD ($) $ / lb
Fair Value, Assets and Liabilities Measured on Recurring Basis, Financial Statement Captions [Line Items]
Other Assets, Current	$ 672				$ 422
Other assets	1,966				2,172
Proceeds from Sale of Other Assets, contingent consideration	102	$ 10
Derivative Liability, Fair Value, Gross Liability	42				48
Investment securities (current and long-term):
Marketable Securities	0
Derivatives:
Derivative Asset	5				16
Derivatives: [Abstract]
Derivative Liability	41				41
Fair Value Measured at Net Asset Value Per Share [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis, Financial Statement Captions [Line Items]
Discontinued Operation, Contingent Receivable	0				0
Investment securities (current and long-term):
Investments, Fair Value Disclosure	27				25
Trust Assets Fair Value Disclosure	59				55
Derivatives:
Derivative Asset	0				0
Derivatives: [Abstract]
Derivative Liability	0				0
Long-term debt, including current portion	0				0
Level 1
Fair Value, Assets and Liabilities Measured on Recurring Basis, Financial Statement Captions [Line Items]
Discontinued Operation, Contingent Receivable	0				0
Investment securities (current and long-term):
Investments, Fair Value Disclosure	4				4
Trust Assets Fair Value Disclosure	4				5
Derivatives:
Derivative Asset	0				0
Derivatives: [Abstract]
Derivative Liability	5				7
Long-term debt, including current portion	0				0
Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis, Financial Statement Captions [Line Items]
Discontinued Operation, Contingent Receivable	0				0
Investment securities (current and long-term):
Investments, Fair Value Disclosure	0				0
Trust Assets Fair Value Disclosure	133				121
Derivatives:
Derivative Asset	73				96
Derivatives: [Abstract]
Derivative Liability	37				41
Long-term debt, including current portion	9,872				10,238
Level 3
Fair Value, Assets and Liabilities Measured on Recurring Basis, Financial Statement Captions [Line Items]
Discontinued Operation, Contingent Receivable	110				127
Investment securities (current and long-term):
Investments, Fair Value Disclosure	0				0
Trust Assets Fair Value Disclosure	0				0
Derivatives:
Derivative Asset	0				0
Derivatives: [Abstract]
Derivative Liability	0				0
Long-term debt, including current portion	0				0
Estimate of Fair Value Measurement [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis, Financial Statement Captions [Line Items]
Discontinued Operation, Contingent Receivable	110				127
Investment securities (current and long-term):
Investments, Fair Value Disclosure	31				29
Trust Assets Fair Value Disclosure	196				181
Derivatives:
Derivative Asset	73				96
Derivatives: [Abstract]
Derivative Liability	42				48
Long-term debt, including current portion	9,872				10,238
Carrying Amount, Fair Value Disclosure [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis, Financial Statement Captions [Line Items]
Discontinued Operation, Contingent Receivable	128				143
Investment securities (current and long-term):
Investments, Fair Value Disclosure	31				29
Trust Assets Fair Value Disclosure	196				181
Derivatives:
Derivative Asset	73				96
Derivatives: [Abstract]
Derivative Liability	42				48
Long-term debt, including current portion	9,919				11,141
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	36				39
Derivatives:
Derivative Asset	5				16
Derivatives: [Abstract]
Derivative Liability	35				32
Embedded Derivative Financial Instruments [Member] | Fair Value Measured at Net Asset Value Per Share [Member]
Derivatives:
Derivative Asset	0				0
Derivatives: [Abstract]
Derivative Liability	0				0
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	6				23
Derivatives: [Abstract]
Derivative Liability	36				39
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	6				23
Derivatives: [Abstract]
Derivative Liability	36				39
Embedded Derivative Financial Instruments [Member] | Carrying Amount, Fair Value Disclosure [Member]
Derivatives:
Derivative Asset	6				23
Derivatives: [Abstract]
Derivative Liability	36				39
Commodity Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis, Financial Statement Captions [Line Items]
Derivative Liability, Fair Value, Gross Liability	6				9
Derivatives:
Derivative Asset	0				0
Derivatives: [Abstract]
Derivative Liability	6				9
Commodity Contract [Member] | Fair Value Measured at Net Asset Value Per Share [Member]
Derivatives: [Abstract]
Derivative Liability	0				0
Commodity Contract [Member] | Level 1
Derivatives: [Abstract]
Derivative Liability	5				7
Commodity Contract [Member] | Level 2
Derivatives: [Abstract]
Derivative Liability	1				2
Commodity Contract [Member] | Level 3
Derivatives: [Abstract]
Derivative Liability	0				0
Commodity Contract [Member] | Estimate of Fair Value Measurement [Member]
Derivatives: [Abstract]
Derivative Liability	6				9
Commodity Contract [Member] | Carrying Amount, Fair Value Disclosure [Member]
Derivatives: [Abstract]
Derivative Liability	6				9
Africa and onshore California [Member] | Commodity Contract [Member] | Fair Value Measured at Net Asset Value Per Share [Member]
Derivatives:
Derivative Asset	0				0
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	67				73
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	67				73
Africa and onshore California [Member] | Commodity Contract [Member] | Carrying Amount, Fair Value Disclosure [Member]
Derivatives:
Derivative Asset	67				73
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	27				25
Trust Assets Fair Value Disclosure	59				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	27				25
Trust Assets Fair Value Disclosure	59				55
U.S. core fixed income fund [Member] | Carrying Amount, Fair Value Disclosure [Member]
Investment securities (current and long-term):
Marketable Securities	27				25
Trust Assets Fair Value Disclosure	59				55
Equity securities | Fair Value Measured at Net Asset Value Per Share [Member]
Investment securities (current and long-term):
Marketable Securities					0
Equity securities | Level 1
Investment securities (current and long-term):
Marketable Securities	4				4
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	4				4
Equity securities | Carrying Amount, Fair Value Disclosure [Member]
Investment securities (current and long-term):
Marketable Securities	4				4
Government bonds | Fair Value Measured at Net Asset Value Per Share [Member]
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure	0				0
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	38				36
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	38				36
Government bonds | Carrying Amount, Fair Value Disclosure [Member]
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure	38				36
Corporate bonds [Member] | Fair Value Measured at Net Asset Value Per Share [Member]
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure	0				0
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	35				28
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	35				28
Corporate bonds [Member] | Carrying Amount, Fair Value Disclosure [Member]
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure	35				28
Government mortgage-backed securities [Member] | Fair Value Measured at Net Asset Value Per Share [Member]
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure	0				0
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	41				38
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	41				38
Government mortgage-backed securities [Member] | Carrying Amount, Fair Value Disclosure [Member]
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure	41				38
Asset-backed securities [Member] | Fair Value Measured at Net Asset Value Per Share [Member]
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure	0				0
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	12				11
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	12				11
Asset-backed securities [Member] | Carrying Amount, Fair Value Disclosure [Member]
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure	12				11
Money market funds [Member] | Fair Value Measured at Net Asset Value Per Share [Member]
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure	0				0
Money market funds [Member] | Level 1
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure	4				5
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	4				5
Money market funds [Member] | Carrying Amount, Fair Value Disclosure [Member]
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure	4				5
Collateralized Mortgage Backed Securities [Member] | Fair Value Measured at Net Asset Value Per Share [Member]
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure	0				0
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	6				7
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	6				7
Collateralized Mortgage Backed Securities [Member] | Carrying Amount, Fair Value Disclosure [Member]
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure	6				7
Municipal bonds [Member] | Fair Value Measured at Net Asset Value Per Share [Member]
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure	0				0
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 Assets, Current	100				109
Other assets	164				126
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	36				39
TF Holdings Limited | Disposed of by sale
Fair Value, Assets and Liabilities Measured on Recurring Basis, Financial Statement Captions [Line Items]
Other Assets, Current	59
Other assets					57
Discontinued Operation, Contingent Receivable							$ 120
Copper | TF Holdings Limited | Disposed of by sale
Fair Value, Assets and Liabilities Measured on Recurring Basis, Financial Statement Captions [Line Items]
Discontinued Operation, Contingent Receivable							60
Cobalt | TF Holdings Limited | Disposed of by sale
Fair Value, Assets and Liabilities Measured on Recurring Basis, Financial Statement Captions [Line Items]
Discontinued Operation, Contingent Receivable							$ 60
Derivatives:
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 assets	8				16
Discontinued Operation, Contingent Receivable						$ 150
Proceeds from Sale of Other Assets, contingent consideration	50
Derivatives:
Discontinued Operation, Contingent Receivable, Per Year					50
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 Assets, Current	18				27
Other assets	$ 110				$ 116
Discontinued Operation, Contingent Receivable						$ 150
Forecast | Freeport-McMoRan Oil & Gas | Onshore California [Member]
Derivatives:
Discontinued Operation, Contingent Receivable, Per Year			$ 50	$ 50
Crude Oil [Member] | Freeport-McMoRan Oil & Gas | Onshore California [Member]
Derivatives:
Contingent consideration, reference threshold (in us dollars per pound) | $ / bbl					70	70
Maximum [Member] | Copper | TF Holdings Limited | Disposed of by sale
Derivatives:
Contingent consideration, reference threshold (in us dollars per pound) | $ / lb							3.50