Income Taxes (Deferred Income Tax Liabilities and Assets) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Deferred Tax Liabilities
Properties, plants and equipment, and intangibles	$ 3,297	$ 3,074
Investment in joint ventures	2,137	2,041
Investment in subsidiaries	794	602
Inventory	0	66
Other	263	14
Total deferred tax liabilities	6,491	5,797
Deferred Tax Assets
Benefit plan accruals	460	395
Asset retirement obligations and accrued environmental costs	115	109
Loss and credit carryforwards	54	59
Other financial accruals and deferrals	70	16
Inventory	28	0
Other	281	0
Total deferred tax assets	1,008	579
Less: valuation allowance	22	8
Net deferred tax assets	986	571
Net deferred tax liabilities	$ 5,505	$ 5,226