Fair Value Measurements, Recurring (Details) - Fair Value, Recurring [Member] - USD ($) $ in Millions	Sep. 30, 2025	Dec. 31, 2024
Assets
Investments in AFS debt securities	$ 27	$ 26
Total gross fair value, assets	458	529
Effect of counterparty netting	(328)	(402)
Effect of cash collateral netting	0	0
Net carrying value on balance sheet, assets	130	127
Liabilities
Blending program obligations	134	13
Total gross fair value, liabilities	482	464
Effect of counterparty netting	(328)	(402)
Effect of cash collateral netting	(13)	(46)
Net carrying value on balance sheet, liabilities	141	16
Assets Held in Trust [Member]
Assets
Investments of certain benefit plans	94	93
Commodity Contracts [Member]
Assets
Derivative contracts	333	402
Effect of counterparty netting	(328)	(402)
Effect of cash collateral netting	0	0
Derivative contracts, net assets	5	0
Cash collateral received not offset	0	0
Liabilities
Derivative contracts	341	448
Effect of counterparty netting	(328)	(402)
Effect of cash collateral netting	(13)	(46)
Derivative contracts, net liabilities	0	0
Cash collateral paid not offset	(66)	(71)
Foreign Currency Contracts [Member]
Assets
Derivative contracts, not subject to netting	4	6
Physical Purchase Contracts [Member]
Assets
Derivative contracts, not subject to netting		2
Liabilities
Derivative contracts, not subject to netting	7	3
Level 1 [Member]
Assets
Investments in AFS debt securities	1	6
Total gross fair value, assets	428	503
Liabilities
Blending program obligations	0	0
Total gross fair value, liabilities	341	448
Level 1 [Member] | Assets Held in Trust [Member]
Assets
Investments of certain benefit plans	90	89
Level 1 [Member] | Commodity Contracts [Member]
Assets
Derivative contracts	333	402
Liabilities
Derivative contracts	341	448
Level 1 [Member] | Foreign Currency Contracts [Member]
Assets
Derivative contracts, not subject to netting	4	6
Level 1 [Member] | Physical Purchase Contracts [Member]
Assets
Derivative contracts, not subject to netting		0
Liabilities
Derivative contracts, not subject to netting	0	0
Level 2 [Member]
Assets
Investments in AFS debt securities	26	20
Total gross fair value, assets	26	22
Liabilities
Blending program obligations	134	13
Total gross fair value, liabilities	141	16
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] | Foreign Currency Contracts [Member]
Assets
Derivative contracts, not subject to netting	0	0
Level 2 [Member] | Physical Purchase Contracts [Member]
Assets
Derivative contracts, not subject to netting		2
Liabilities
Derivative contracts, not subject to netting	7	3
Level 3 [Member]
Assets
Investments in AFS debt securities	0	0
Total gross fair value, assets	4	4
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] | Foreign Currency Contracts [Member]
Assets
Derivative contracts, not subject to netting	0	0
Level 3 [Member] | Physical Purchase Contracts [Member]
Assets
Derivative contracts, not subject to netting		0
Liabilities
Derivative contracts, not subject to netting	$ 0	$ 0