Fair Value Measurements, Recurring (Details) - Fair Value, Recurring [Member] - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Assets
Total gross fair value, assets	$ 758	$ 718
Effect of counterparty netting	(506)	(612)
Effect of cash collateral netting	(38)	0
Net carrying value on Balance Sheet, assets	214	106
Liabilities
Environmental credit obligations	38	2
Total gross fair value, liabilities	568	683
Effect of counterparty netting	(506)	(612)
Effect of cash collateral netting	(13)	(56)
Net carrying value on Balance Sheet, liabilities	49	15
Assets Held in Trust [Member]
Assets
Investments of certain benefit plans	73	74
Commodity Contracts [Member]
Assets
Derivative contracts	656	617
Effect of counterparty netting	(506)	(612)
Effect of cash collateral netting	(38)	0
Derivative contracts, net assets	112	5
Cash collateral received not offset	0	0
Liabilities
Derivative contracts	519	668
Effect of counterparty netting	(506)	(612)
Effect of cash collateral netting	(13)	(56)
Derivative contracts, net liabilities	0	0
Cash collateral paid not offset	(38)	(84)
Physical Purchase Contracts [Member]
Assets
Derivative contracts	1
Derivative contracts, net assets	1
Liabilities
Derivative contracts	2	3
Derivative contracts, net liabilities	2	3
Foreign Currency Contracts [Member]
Assets
Derivative contracts	28	27
Derivative contracts, net assets	28	27
Liabilities
Derivative contracts	9	10
Derivative contracts, net liabilities	9	10
Fair Value, Inputs, Level 1 [Member]
Assets
Total gross fair value, assets	749	709
Liabilities
Environmental credit obligations	0	0
Total gross fair value, liabilities	528	678
Fair Value, Inputs, Level 1 [Member] | Assets Held in Trust [Member]
Assets
Investments of certain benefit plans	65	65
Fair Value, Inputs, Level 1 [Member] | Commodity Contracts [Member]
Assets
Derivative contracts	656	617
Liabilities
Derivative contracts	519	668
Fair Value, Inputs, Level 1 [Member] | Physical Purchase Contracts [Member]
Assets
Derivative contracts	0
Liabilities
Derivative contracts	0	0
Fair Value, Inputs, Level 1 [Member] | Foreign Currency Contracts [Member]
Assets
Derivative contracts	28	27
Liabilities
Derivative contracts	9	10
Fair Value, Inputs, Level 2 [Member]
Assets
Total gross fair value, assets	1	0
Liabilities
Environmental credit obligations	38	2
Total gross fair value, liabilities	40	5
Fair Value, Inputs, Level 2 [Member] | Assets Held in Trust [Member]
Assets
Investments of certain benefit plans	0	0
Fair Value, Inputs, Level 2 [Member] | Commodity Contracts [Member]
Assets
Derivative contracts	0	0
Liabilities
Derivative contracts	0	0
Fair Value, Inputs, Level 2 [Member] | Physical Purchase Contracts [Member]
Assets
Derivative contracts	1
Liabilities
Derivative contracts	2	3
Fair Value, Inputs, Level 2 [Member] | Foreign Currency Contracts [Member]
Assets
Derivative contracts	0	0
Liabilities
Derivative contracts	0	0
Fair Value, Inputs, Level 3 [Member]
Assets
Total gross fair value, assets	8	9
Liabilities
Environmental credit obligations	0	0
Total gross fair value, liabilities	0	0
Fair Value, Inputs, Level 3 [Member] | Assets Held in Trust [Member]
Assets
Investments of certain benefit plans	8	9
Fair Value, Inputs, Level 3 [Member] | Commodity Contracts [Member]
Assets
Derivative contracts	0	0
Liabilities
Derivative contracts	0	0
Fair Value, Inputs, Level 3 [Member] | Physical Purchase Contracts [Member]
Assets
Derivative contracts	0
Liabilities
Derivative contracts	0	0
Fair Value, Inputs, Level 3 [Member] | Foreign Currency Contracts [Member]
Assets
Derivative contracts	0	0
Liabilities
Derivative contracts	$ 0	$ 0