Fair Value Measurements, Recurring (Details) - Fair Value, Recurring [Member] - USD ($) $ in Millions	Sep. 30, 2026	Dec. 31, 2025
Assets
Clean fuel production credits	$ 87	$ 55
Investments in AFS debt securities	28	27
Total gross fair value, assets	2,841	669
Effect of counterparty netting	(2,552)	(448)
Effect of cash collateral netting	(19)	(7)
Net carrying value on balance sheet, assets	270	214
Liabilities
Blending program obligations	53	85
Total gross fair value, liabilities	3,174	544
Effect of counterparty netting	(2,552)	(448)
Effect of cash collateral netting	(564)	(5)
Net carrying value on balance sheet, liabilities	58	91
Assets Held in Trust [Member]
Assets
Investments of certain benefit plans	100	96
Commodity Contracts [Member]
Assets
Commodity derivative contracts	2,602	490
Effect of counterparty netting	(2,552)	(448)
Effect of cash collateral netting	(19)	(7)
Commodity derivative contracts, net assets	31	35
Cash collateral received not offset	0	0
Liabilities
Commodity derivative contracts	3,116	453
Effect of counterparty netting	(2,552)	(448)
Effect of cash collateral netting	(564)	(5)
Commodity derivative contracts, net liabilities	0	0
Cash collateral paid not offset	(124)	(39)
Physical Purchase Contracts [Member]
Assets
Derivative contracts, not subject to netting	11	1
Liabilities
Derivative contracts, not subject to netting	5	4
Foreign Currency Contracts [Member]
Assets
Derivative contracts, not subject to netting	13
Liabilities
Derivative contracts, not subject to netting		2
Level 1 [Member]
Assets
Clean fuel production credits	0	0
Investments in AFS debt securities	2	1
Total gross fair value, assets	2,713	583
Liabilities
Blending program obligations	0	0
Total gross fair value, liabilities	3,116	455
Level 1 [Member] | Assets Held in Trust [Member]
Assets
Investments of certain benefit plans	96	92
Level 1 [Member] | Commodity Contracts [Member]
Assets
Commodity derivative contracts	2,602	490
Liabilities
Commodity derivative contracts	3,116	453
Level 1 [Member] | Physical Purchase Contracts [Member]
Assets
Derivative contracts, not subject to netting	0	0
Liabilities
Derivative contracts, not subject to netting	0	0
Level 1 [Member] | Foreign Currency Contracts [Member]
Assets
Derivative contracts, not subject to netting	13
Liabilities
Derivative contracts, not subject to netting		2
Level 2 [Member]
Assets
Clean fuel production credits	0	0
Investments in AFS debt securities	26	26
Total gross fair value, assets	37	27
Liabilities
Blending program obligations	53	85
Total gross fair value, liabilities	58	89
Level 2 [Member] | Assets Held in Trust [Member]
Assets
Investments of certain benefit plans	0	0
Level 2 [Member] | Commodity Contracts [Member]
Assets
Commodity derivative contracts	0	0
Liabilities
Commodity derivative contracts	0	0
Level 2 [Member] | Physical Purchase Contracts [Member]
Assets
Derivative contracts, not subject to netting	11	1
Liabilities
Derivative contracts, not subject to netting	5	4
Level 2 [Member] | Foreign Currency Contracts [Member]
Assets
Derivative contracts, not subject to netting	0
Liabilities
Derivative contracts, not subject to netting		0
Level 3 [Member]
Assets
Clean fuel production credits	87	55
Investments in AFS debt securities	0	0
Total gross fair value, assets	91	59
Liabilities
Blending program obligations	0	0
Total gross fair value, liabilities	0	0
Level 3 [Member] | Assets Held in Trust [Member]
Assets
Investments of certain benefit plans	4	4
Level 3 [Member] | Commodity Contracts [Member]
Assets
Commodity derivative contracts	0	0
Liabilities
Commodity derivative contracts	0	0
Level 3 [Member] | Physical Purchase Contracts [Member]
Assets
Derivative contracts, not subject to netting	0	0
Liabilities
Derivative contracts, not subject to netting	0	0
Level 3 [Member] | Foreign Currency Contracts [Member]
Assets
Derivative contracts, not subject to netting	$ 0
Liabilities
Derivative contracts, not subject to netting		$ 0