Income Taxes, Deferred Income Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Deferred income tax assets:
Tax credit carryforwards	$ 644	$ 69
Net operating losses (NOLs)	523	492
Inventories	101	135
Compensation and employee benefit liabilities	175	179
Environmental liabilities	71	47
Other	141	112
Total deferred income tax assets	1,655	1,034
Valuation allowance	(1,111)	(498)
Net deferred income tax assets	544	536
Deferred income tax liabilities:
Property, plant, and equipment	4,589	4,545
Deferred turnaround costs	316	272
Inventories	287	243
Investments	142	77
Other	172	107
Total deferred income tax liabilities	5,506	5,244
Net deferred income tax liabilities	$ 4,962	$ 4,708