Fair Value Measurements, Recurring (Details) - Fair Value, Recurring [Member] - USD ($) $ in Millions	Mar. 31, 2026	Dec. 31, 2025
Assets
Clean fuel production credits	$ 140	$ 55
Investments in AFS debt securities	28	27
Total gross fair value, assets	5,473	669
Effect of counterparty netting	(5,100)	(448)
Effect of cash collateral netting	0	(7)
Net carrying value on balance sheet, assets	373	214
Liabilities
Blending program obligations	149	85
Total gross fair value, liabilities	5,600	544
Effect of counterparty netting	(5,100)	(448)
Effect of cash collateral netting	(344)	(5)
Net carrying value on balance sheet, liabilities	156	91
Assets Held in Trust [Member]
Assets
Investments of certain benefit plans	94	96
Commodity Contracts [Member]
Assets
Derivative contracts	5,199	490
Effect of counterparty netting	(5,100)	(448)
Effect of cash collateral netting	0	(7)
Derivative contracts, net assets	99	35
Cash collateral received not offset	0	0
Liabilities
Derivative contracts	5,444	453
Effect of counterparty netting	(5,100)	(448)
Effect of cash collateral netting	(344)	(5)
Derivative contracts, net liabilities	0	0
Cash collateral paid not offset	(166)	(39)
Physical Purchase Contracts [Member]
Assets
Derivative contracts, not subject to netting	2	1
Liabilities
Derivative contracts, not subject to netting	7	4
Foreign Currency Contracts [Member]
Assets
Derivative contracts, not subject to netting	10
Liabilities
Derivative contracts, not subject to netting		2
Level 1 [Member]
Assets
Clean fuel production credits	0	0
Investments in AFS debt securities	0	1
Total gross fair value, assets	5,299	583
Liabilities
Blending program obligations	0	0
Total gross fair value, liabilities	5,444	455
Level 1 [Member] | Assets Held in Trust [Member]
Assets
Investments of certain benefit plans	90	92
Level 1 [Member] | Commodity Contracts [Member]
Assets
Derivative contracts	5,199	490
Liabilities
Derivative contracts	5,444	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	10
Liabilities
Derivative contracts, not subject to netting		2
Level 2 [Member]
Assets
Clean fuel production credits	0	0
Investments in AFS debt securities	28	26
Total gross fair value, assets	30	27
Liabilities
Blending program obligations	149	85
Total gross fair value, liabilities	156	89
Level 2 [Member] | Assets Held in Trust [Member]
Assets
Investments of certain benefit plans	0	0
Level 2 [Member] | Commodity Contracts [Member]
Assets
Derivative contracts	0	0
Liabilities
Derivative contracts	0	0
Level 2 [Member] | Physical Purchase Contracts [Member]
Assets
Derivative contracts, not subject to netting	2	1
Liabilities
Derivative contracts, not subject to netting	7	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	140	55
Investments in AFS debt securities	0	0
Total gross fair value, assets	144	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
Derivative contracts	0	0
Liabilities
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