Fair Value Measurements, Recurring (Details) - Fair Value, Recurring [Member] - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Assets
Total gross fair value, assets	$ 488	$ 718
Effect of counterparty netting	(347)	(612)
Effect of cash collateral netting	(20)	0
Net carrying value on Balance Sheet, assets	121	106
Liabilities
Environmental credit obligations	23	2
Total gross fair value, liabilities	373	683
Effect of counterparty netting	(347)	(612)
Effect of cash collateral netting	0	(56)
Net carrying value on Balance Sheet, liabilities	26	15
Assets Held in Trust [Member]
Assets
Investments of certain benefit plans	79	74
Commodity Contracts [Member]
Assets
Derivative contracts	398	617
Effect of counterparty netting	(347)	(612)
Effect of cash collateral netting	(20)	0
Derivative contracts, net assets	31	5
Cash collateral received not offset	0	0
Liabilities
Derivative contracts	347	668
Effect of counterparty netting	(347)	(612)
Effect of cash collateral netting	0	(56)
Derivative contracts, net liabilities	0	0
Cash collateral paid not offset	(39)	(84)
Physical Purchase Contracts [Member]
Assets
Derivative contracts	2
Derivative contracts, net assets	2
Liabilities
Derivative contracts	0	3
Derivative contracts, net liabilities	0	3
Foreign Currency Contracts [Member]
Assets
Derivative contracts	9	27
Derivative contracts, net assets	9	27
Liabilities
Derivative contracts	3	10
Derivative contracts, net liabilities	3	10
Fair Value, Inputs, Level 1 [Member]
Assets
Total gross fair value, assets	478	709
Liabilities
Environmental credit obligations	0	0
Total gross fair value, liabilities	350	678
Fair Value, Inputs, Level 1 [Member] | Assets Held in Trust [Member]
Assets
Investments of certain benefit plans	71	65
Fair Value, Inputs, Level 1 [Member] | Commodity Contracts [Member]
Assets
Derivative contracts	398	617
Liabilities
Derivative contracts	347	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	9	27
Liabilities
Derivative contracts	3	10
Fair Value, Inputs, Level 2 [Member]
Assets
Total gross fair value, assets	2	0
Liabilities
Environmental credit obligations	23	2
Total gross fair value, liabilities	23	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	2
Liabilities
Derivative contracts	0	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