Income Taxes, Deferred Income Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Deferred income tax assets:
Tax credit carryforwards	$ 683	$ 644
Net operating losses (NOLs)	582	523
Inventories	141	101
Compensation and employee benefit liabilities	213	175
Environmental liabilities	69	71
Other	156	141
Total deferred income tax assets	1,844	1,655
Valuation allowance	(1,200)	(1,111)
Net deferred income tax assets	644	544
Deferred income tax liabilities:
Property, plant, and equipment	4,924	4,589
Deferred turnaround costs	331	316
Inventories	217	287
Investments	122	142
Other	153	172
Total deferred income tax liabilities	5,747	5,506
Net deferred income tax liabilities	$ 5,103	$ 4,962