Fair Value Measurement (Fair Value Measurement Inputs) (Details) $ in Millions	3 Months Ended	6 Months Ended		12 Months Ended
	Mar. 31, 2019 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 $ / bbl	Dec. 31, 2016 USD ($) $ / bbl
Fair Value, Assets and Liabilities Measured on Recurring Basis, Financial Statement Captions [Line Items]
Other Assets, Current		$ 517			$ 655
Other assets		1,693			1,885
Proceeds from Sale of Other Assets, contingent consideration		116	$ 94
Derivative Liability, Fair Value, Gross Liability		34			21
Investment securities (current and long-term):
Marketable Securities		0
Derivatives:
Derivative Asset		90			74
Derivatives: [Abstract]
Derivative Liability		30			21
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		29			27
Trust Assets Fair Value Disclosure		63			59
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		5			4
Trust Assets Fair Value Disclosure		9			3
Derivatives:
Derivative Asset		13			5
Derivatives: [Abstract]
Derivative Liability		2			0
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		136			134
Derivatives:
Derivative Asset		81			80
Derivatives: [Abstract]
Derivative Liability		32			21
Long-term debt, including current portion		10,013			10,239
Level 3
Fair Value, Assets and Liabilities Measured on Recurring Basis, Financial Statement Captions [Line Items]
Discontinued Operation, Contingent Receivable		78			108
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		78			108
Investment securities (current and long-term):
Investments, Fair Value Disclosure		34			31
Trust Assets Fair Value Disclosure		208			196
Derivatives:
Derivative Asset		94			85
Derivatives: [Abstract]
Derivative Liability		34			21
Long-term debt, including current portion		10,013			10,239
Carrying Amount, Fair Value Disclosure [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis, Financial Statement Captions [Line Items]
Discontinued Operation, Contingent Receivable		115			122
Investment securities (current and long-term):
Investments, Fair Value Disclosure		34			31
Trust Assets Fair Value Disclosure		208			196
Derivatives:
Derivative Asset		94			85
Derivatives: [Abstract]
Derivative Liability		34			21
Long-term debt, including current portion		9,914			9,826
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		28			20
Derivatives:
Derivative Asset		77			68
Derivatives: [Abstract]
Derivative Liability		28			20
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		77			68
Derivatives: [Abstract]
Derivative Liability		28			20
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		77			68
Derivatives: [Abstract]
Derivative Liability		28			20
Embedded Derivative Financial Instruments [Member] | Carrying Amount, Fair Value Disclosure [Member]
Derivatives:
Derivative Asset		77			68
Derivatives: [Abstract]
Derivative Liability		28			20
Forward Contracts [Member] | Level 1
Derivatives:
Derivative Asset		2
Forward Contracts [Member] | Level 2
Derivatives:
Derivative Asset		2
Forward Contracts [Member] | Level 3
Derivatives:
Derivative Asset		0
Forward Contracts [Member] | Estimate of Fair Value Measurement [Member]
Derivatives:
Derivative Asset		4
Forward Contracts [Member] | Carrying Amount, Fair Value Disclosure [Member]
Derivatives:
Derivative Asset		4
Commodity Contract [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis, Financial Statement Captions [Line Items]
Derivative Liability, Fair Value, Gross Liability		6			1
Derivatives:
Derivative Asset		13			6
Derivatives: [Abstract]
Derivative Liability		2			1
Commodity Contract [Member] | Fair Value Measured at Net Asset Value Per Share [Member]
Derivatives:
Derivative Asset		0			0
Derivatives: [Abstract]
Derivative Liability		0			0
Commodity Contract [Member] | Level 1
Derivatives:
Derivative Asset					5
Derivatives: [Abstract]
Derivative Liability		2			0
Commodity Contract [Member] | Level 2
Derivatives:
Derivative Asset					1
Derivatives: [Abstract]
Derivative Liability		4			1
Commodity Contract [Member] | Level 3
Derivatives:
Derivative Asset					0
Derivatives: [Abstract]
Derivative Liability		0			0
Commodity Contract [Member] | Estimate of Fair Value Measurement [Member]
Derivatives:
Derivative Asset					6
Derivatives: [Abstract]
Derivative Liability		6			1
Commodity Contract [Member] | Carrying Amount, Fair Value Disclosure [Member]
Derivatives:
Derivative Asset					6
Derivatives: [Abstract]
Derivative Liability		6			1
Future [Member] | Level 1
Derivatives:
Derivative Asset		11
Future [Member] | Level 2
Derivatives:
Derivative Asset		2
Future [Member] | Level 3
Derivatives:
Derivative Asset		0
Future [Member] | Estimate of Fair Value Measurement [Member]
Derivatives:
Derivative Asset		13
Future [Member] | Carrying Amount, Fair Value Disclosure [Member]
Derivatives:
Derivative Asset		13
Africa and onshore California [Member] | Commodity Contract [Member] | Fair Value Measured at Net Asset Value Per Share [Member]
Derivatives:
Derivative Asset					0
Africa and onshore California [Member] | Commodity Contract [Member] | Level 1
Derivatives:
Derivative Asset					0
Africa and onshore California [Member] | Commodity Contract [Member] | Level 2
Derivatives:
Derivative Asset					11
Africa and onshore California [Member] | Commodity Contract [Member] | Level 3
Derivatives:
Derivative Asset					0
Africa and onshore California [Member] | Commodity Contract [Member] | Estimate of Fair Value Measurement [Member]
Derivatives:
Derivative Asset					11
Africa and onshore California [Member] | Commodity Contract [Member] | Carrying Amount, Fair Value Disclosure [Member]
Derivatives:
Derivative Asset					11
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		29			27
Trust Assets Fair Value Disclosure		63			59
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		29			27
Trust Assets Fair Value Disclosure		63			59
U.S. core fixed income fund [Member] | Carrying Amount, Fair Value Disclosure [Member]
Investment securities (current and long-term):
Marketable Securities		29			27
Trust Assets Fair Value Disclosure		63			59
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		5			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		5			4
Equity securities | Carrying Amount, Fair Value Disclosure [Member]
Investment securities (current and long-term):
Marketable Securities		5			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		32			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		32			36
Government bonds | Carrying Amount, Fair Value Disclosure [Member]
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure		32			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		45			33
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		45			33
Corporate bonds [Member] | Carrying Amount, Fair Value Disclosure [Member]
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure		45			33
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		40			43
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		40			43
Government mortgage-backed securities [Member] | Carrying Amount, Fair Value Disclosure [Member]
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure		40			43
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		14			14
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			14
Asset-backed securities [Member] | Carrying Amount, Fair Value Disclosure [Member]
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure		14			14
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		9			3
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		9			3
Money market funds [Member] | Carrying Amount, Fair Value Disclosure [Member]
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure		9			3
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		4			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		4			7
Collateralized Mortgage Backed Securities [Member] | Carrying Amount, Fair Value Disclosure [Member]
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure		4			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		132			100
Other assets		131			157
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		28			20
Freeport-McMoRan Oil & Gas | Onshore California [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis, Financial Statement Captions [Line Items]
Other assets		0			11
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		12			18
Other assets		103			$ 104
Discontinued Operation, Contingent Receivable							$ 150
Forecast | Freeport-McMoRan Oil & Gas | Onshore California [Member]
Derivatives:
Discontinued Operation, Contingent Receivable, Per Year				$ 50
Crude Oil [Member] | Freeport-McMoRan Oil & Gas | Onshore California [Member]
Derivatives:
Contingent consideration, reference threshold (in us dollars per pound) | $ / bbl						70	70
Fair Value, Recurring [Member] | Forward Contracts [Member] | Estimate of Fair Value Measurement [Member]
Derivatives:
Derivative Asset		$ 0