Fair Value Measurement - Fair Value Measurement Inputs (Details) - USD ($) $ in Millions	3 Months Ended
	Sep. 30, 2024	Dec. 31, 2023	Dec. 31, 2016
Investment securities (current and long-term):
Other assets	$ 1,848	$ 1,810
Other Assets, Current	436	375
Derivatives:
Derivative Asset	132	80
Derivatives: [Abstract]
Derivative Liability	31	24
Restricted cash and cash equivalents	1,117	1,208
Designated For Export Proceeds
Derivatives: [Abstract]
Restricted cash and cash equivalents	1,000	1,100
Deepwater Gulf of Mexico Interests | Freeport-McMoRan Oil & Gas
Derivatives:
Discontinued Operation, Contingent Receivable	4		$ 150
Derivatives: [Abstract]
Royalty interest payable	1	12
Net impairment	32
Contingent consideration impairment loss	42
Decrease to royalty interest payable	10
Fair Value Measured at Net Asset Value Per Share
Investment securities (current and long-term):
Investments, Fair Value Disclosure	28	27
Trust Assets Fair Value Disclosure	68	65
Derivatives:
Derivative Asset	0	0
Discontinued Operation, Contingent Receivable	0	0
Derivatives: [Abstract]
Derivative Liability	0	0
Long-term debt, including current portion	0	0
Level 1
Investment securities (current and long-term):
Investments, Fair Value Disclosure	9	6
Trust Assets Fair Value Disclosure	21	17
Derivatives:
Derivative Asset	16	3
Discontinued Operation, Contingent Receivable	0	0
Derivatives: [Abstract]
Derivative Liability	14	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	133	130
Derivatives:
Derivative Asset	119	77
Discontinued Operation, Contingent Receivable	0	0
Derivatives: [Abstract]
Derivative Liability	20	23
Long-term debt, including current portion	9,877	9,364
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
Discontinued Operation, Contingent Receivable	4	42
Derivatives: [Abstract]
Derivative Liability	0	0
Long-term debt, including current portion	0	0
Estimate of Fair Value Measurement
Investment securities (current and long-term):
Investments, Fair Value Disclosure	37	33
Trust Assets Fair Value Disclosure	222	212
Derivatives:
Derivative Asset	135	80
Discontinued Operation, Contingent Receivable	4	42
Derivatives: [Abstract]
Derivative Liability	34	24
Long-term debt, including current portion	9,877	9,364
Carrying Amount, Fair Value Disclosure
Investment securities (current and long-term):
Investments, Fair Value Disclosure	37	33
Trust Assets Fair Value Disclosure	222	212
Derivatives:
Derivative Asset	135	80
Discontinued Operation, Contingent Receivable	4	50
Derivatives: [Abstract]
Derivative Liability	34	24
Long-term debt, including current portion	9,679	9,422
Embedded Derivative Financial Instruments
Derivatives:
Derivative Asset	105	76
Derivatives: [Abstract]
Derivative Liability	8	23
Embedded Derivative Financial Instruments | Fair Value Measured at Net Asset Value Per Share
Derivatives:
Derivative Asset	0	0
Derivatives: [Abstract]
Derivative Liability	0	0
Embedded Derivative Financial Instruments | Level 1
Derivatives:
Derivative Asset	0	0
Derivatives: [Abstract]
Derivative Liability	0	0
Embedded Derivative Financial Instruments | Level 2
Derivatives:
Derivative Asset	108	76
Derivatives: [Abstract]
Derivative Liability	11	23
Embedded Derivative Financial Instruments | Level 3
Derivatives:
Derivative Asset	0	0
Derivatives: [Abstract]
Derivative Liability	0	0
Embedded Derivative Financial Instruments | Estimate of Fair Value Measurement
Derivatives:
Derivative Asset	108	76
Derivatives: [Abstract]
Derivative Liability	11	23
Embedded Derivative Financial Instruments | Carrying Amount, Fair Value Disclosure
Derivatives:
Derivative Asset	108	76
Derivatives: [Abstract]
Derivative Liability	11	23
Commodity Contract
Derivatives:
Derivative Asset	27	4
Derivatives: [Abstract]
Derivative Liability	23	1
Commodity Contract | Fair Value Measured at Net Asset Value Per Share | Futures and Swaps
Derivatives:
Derivative Asset	0	0
Commodity Contract | Fair Value Measured at Net Asset Value Per Share | Forward Contracts
Derivatives: [Abstract]
Derivative Liability	0	0
Commodity Contract | Level 1 | Futures and Swaps
Derivatives:
Derivative Asset	16	3
Commodity Contract | Level 1 | Forward Contracts
Derivatives: [Abstract]
Derivative Liability	14	1
Commodity Contract | Level 2 | Futures and Swaps
Derivatives:
Derivative Asset	11	1
Commodity Contract | Level 2 | Forward Contracts
Derivatives: [Abstract]
Derivative Liability	9	0
Commodity Contract | Level 3 | Futures and Swaps
Derivatives:
Derivative Asset	0	0
Commodity Contract | Level 3 | Forward Contracts
Derivatives: [Abstract]
Derivative Liability	0	0
Commodity Contract | Estimate of Fair Value Measurement | Futures and Swaps
Derivatives:
Derivative Asset	27	4
Commodity Contract | Estimate of Fair Value Measurement | Forward Contracts
Derivatives: [Abstract]
Derivative Liability	23	1
Commodity Contract | Carrying Amount, Fair Value Disclosure | Futures and Swaps
Derivatives:
Derivative Asset	27	4
Commodity Contract | Carrying Amount, Fair Value Disclosure | Forward Contracts
Derivatives: [Abstract]
Derivative Liability	23	1
U.S. core fixed income fund | Fair Value Measured at Net Asset Value Per Share
Investment securities (current and long-term):
Marketable Securities	28	27
Trust Assets Fair Value Disclosure	68	65
U.S. core fixed income fund | 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 | 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 | 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 | Estimate of Fair Value Measurement
Investment securities (current and long-term):
Marketable Securities	28	27
Trust Assets Fair Value Disclosure	68	65
U.S. core fixed income fund | Carrying Amount, Fair Value Disclosure
Investment securities (current and long-term):
Marketable Securities	28	27
Trust Assets Fair Value Disclosure	68	65
Equity securities | Fair Value Measured at Net Asset Value Per Share
Investment securities (current and long-term):
Marketable Securities	0	0
Equity securities | Level 1
Investment securities (current and long-term):
Marketable Securities	9	6
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
Investment securities (current and long-term):
Marketable Securities	9	6
Equity securities | Carrying Amount, Fair Value Disclosure
Investment securities (current and long-term):
Marketable Securities	9	6
Government mortgage-backed securities | Fair Value Measured at Net Asset Value Per Share
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure	0	0
Government mortgage-backed securities | Level 1
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure	0	0
Government mortgage-backed securities | Level 2
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure	52	51
Government mortgage-backed securities | Level 3
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure	0	0
Government mortgage-backed securities | Estimate of Fair Value Measurement
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure	52	51
Government mortgage-backed securities | Carrying Amount, Fair Value Disclosure
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure	52	51
Corporate bonds | Fair Value Measured at Net Asset Value Per Share
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure	0	0
Corporate bonds | Level 1
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure	0	0
Corporate bonds | Level 2
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure	36	29
Corporate bonds | Level 3
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure	0	0
Corporate bonds | Estimate of Fair Value Measurement
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure	36	29
Corporate bonds | Carrying Amount, Fair Value Disclosure
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure	36	29
Government bonds | Fair Value Measured at Net Asset Value Per Share
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	30	37
Government bonds | Level 3
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure	0	0
Government bonds | Estimate of Fair Value Measurement
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure	30	37
Government bonds | Carrying Amount, Fair Value Disclosure
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure	30	37
Money market funds | Fair Value Measured at Net Asset Value Per Share
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure	0	0
Money market funds | Level 1
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure	21	17
Money market funds | Level 2
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure	0	0
Money market funds | Level 3
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure	0	0
Money market funds | Estimate of Fair Value Measurement
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure	21	17
Money market funds | Carrying Amount, Fair Value Disclosure
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure	21	17
Asset-backed securities | Fair Value Measured at Net Asset Value Per Share
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure	0	0
Asset-backed securities | Level 1
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure	0	0
Asset-backed securities | Level 2
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure	14	12
Asset-backed securities | Level 3
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure	0	0
Asset-backed securities | Estimate of Fair Value Measurement
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure	14	12
Asset-backed securities | Carrying Amount, Fair Value Disclosure
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure	14	12
Collateralized Mortgage Backed Securities | Fair Value Measured at Net Asset Value Per Share
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure	0	0
Collateralized Mortgage Backed Securities | Level 1
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure	0	0
Collateralized Mortgage Backed Securities | Level 2
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure	1	1
Collateralized Mortgage Backed Securities | Level 3
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure	0	0
Collateralized Mortgage Backed Securities | Estimate of Fair Value Measurement
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure	1	1
Collateralized Mortgage Backed Securities | Carrying Amount, Fair Value Disclosure
Investment securities (current and long-term):
Trust Assets Fair Value Disclosure	1	1
Bank Time Deposits | Carrying Amount, Fair Value Disclosure
Investment securities (current and long-term):
Other assets	100	100
Other Assets, Current	$ 100	$ 100