Fair Value Measurements, Recurring (Details) - Fair Value, Recurring [Member] - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Assets
Total gross fair value, assets	$ 4,325	$ 718
Effect of counterparty netting	(4,162)	(612)
Effect of cash collateral netting	(73)	0
Net carrying value on Balance Sheet, assets	90	106
Liabilities
Environmental credit obligations	43	2
Total gross fair value, liabilities	4,593	683
Effect of counterparty netting	(4,162)	(612)
Effect of cash collateral netting	(306)	(56)
Net carrying value on Balance Sheet, liabilities	125	15
Assets Held in Trust [Member]
Assets
Investments of certain benefit plans	71	74
Commodity Contracts [Member]
Assets
Derivative contracts	4,252	617
Effect of counterparty netting	(4,162)	(612)
Effect of cash collateral netting	(73)	0
Derivative contracts, net assets	17	5
Cash collateral received not offset	0	0
Liabilities
Derivative contracts	4,468	668
Effect of counterparty netting	(4,162)	(612)
Effect of cash collateral netting	(306)	(56)
Derivative contracts, net liabilities	0	0
Cash collateral paid not offset	(13)	(84)
Physical Purchase Contracts [Member]
Liabilities
Derivative contracts	10	3
Derivative contracts, net liabilities	10	3
Foreign Currency Contracts [Member]
Assets
Derivative contracts	2	27
Derivative contracts, net assets	2	27
Liabilities
Derivative contracts	72	10
Derivative contracts, net liabilities	72	10
Fair Value, Inputs, Level 1 [Member]
Assets
Total gross fair value, assets	4,316	709
Liabilities
Environmental credit obligations	0	0
Total gross fair value, liabilities	4,540	678
Fair Value, Inputs, Level 1 [Member] | Assets Held in Trust [Member]
Assets
Investments of certain benefit plans	62	65
Fair Value, Inputs, Level 1 [Member] | Commodity Contracts [Member]
Assets
Derivative contracts	4,252	617
Liabilities
Derivative contracts	4,468	668
Fair Value, Inputs, Level 1 [Member] | Physical Purchase Contracts [Member]
Liabilities
Derivative contracts	0	0
Fair Value, Inputs, Level 1 [Member] | Foreign Currency Contracts [Member]
Assets
Derivative contracts	2	27
Liabilities
Derivative contracts	72	10
Fair Value, Inputs, Level 2 [Member]
Assets
Total gross fair value, assets	0	0
Liabilities
Environmental credit obligations	43	2
Total gross fair value, liabilities	53	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]
Liabilities
Derivative contracts	10	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	9	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	9	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]
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