Fair Value Measurements, Recurring (Details) - Fair Value, Measurements, Recurring [Member] - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Assets:
Investments of certain benefit plans	$ 69	$ 73
Total gross fair value, assets	2,865	967
Effect of Counter- party Netting	(2,669)	(893)
Effect of Cash Collateral Netting	(34)	0
Net Carrying Value on Balance Sheet, Assets	162	74
Liabilities:
Environmental credit obligations	13	104
Total gross fair value, liabilities	2,700	1,086
Effect of Counter- party Netting	(2,669)	(893)
Effect of Cash Collateral Netting	(12)	(76)
Net Carrying Value on Balance Sheet, Liabilities	19	117
Commodity Contracts [Member]
Assets:
Derivative contracts	2,792	894
Effect of Counter- party Netting	(2,669)	(893)
Effect of Cash Collateral Netting	(34)	0
Derivative contracts, net assets	89	1
Cash Collateral Received Not Offset	0	0
Liabilities:
Derivative contracts	2,681	969
Effect of Counter- party Netting	(2,669)	(893)
Effect of Cash Collateral Netting	(12)	(76)
Derivative contracts, net liabilities	0	0
Cash Collateral Paid Not Offset	(136)	(102)
Foreign Currency Contracts [Member]
Assets:
Derivative contracts	4
Derivative contracts, net assets	4
Liabilities:
Derivative contracts	1	7
Derivative contracts, net liabilities	1	7
Physical Purchase Contracts [Member]
Liabilities:
Derivative contracts	5	6
Derivative contracts, net liabilities	5	6
Fair Value, Inputs, Level 1 [Member]
Assets:
Investments of certain benefit plans	60	65
Total gross fair value, assets	2,856	940
Liabilities:
Environmental credit obligations	0	0
Total gross fair value, liabilities	2,682	962
Fair Value, Inputs, Level 1 [Member] | Commodity Contracts [Member]
Assets:
Derivative contracts	2,792	875
Liabilities:
Derivative contracts	2,681	955
Fair Value, Inputs, Level 1 [Member] | Foreign Currency Contracts [Member]
Assets:
Derivative contracts	4
Liabilities:
Derivative contracts	1	7
Fair Value, Inputs, Level 1 [Member] | Physical Purchase Contracts [Member]
Liabilities:
Derivative contracts	0	0
Fair Value, Inputs, Level 2 [Member]
Assets:
Investments of certain benefit plans	0	0
Total gross fair value, assets	0	19
Liabilities:
Environmental credit obligations	13	104
Total gross fair value, liabilities	18	124
Fair Value, Inputs, Level 2 [Member] | Commodity Contracts [Member]
Assets:
Derivative contracts	0	19
Liabilities:
Derivative contracts	0	14
Fair Value, Inputs, Level 2 [Member] | Foreign Currency Contracts [Member]
Assets:
Derivative contracts	0
Liabilities:
Derivative contracts	0	0
Fair Value, Inputs, Level 2 [Member] | Physical Purchase Contracts [Member]
Liabilities:
Derivative contracts	5	6
Fair Value, Inputs, Level 3 [Member]
Assets:
Investments of certain benefit plans	9	8
Total gross fair value, assets	9	8
Liabilities:
Environmental credit obligations	0	0
Total gross fair value, liabilities	0	0
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] | Foreign Currency Contracts [Member]
Assets:
Derivative contracts	0
Liabilities:
Derivative contracts	0	0
Fair Value, Inputs, Level 3 [Member] | Physical Purchase Contracts [Member]
Liabilities:
Derivative contracts	$ 0	$ 0