Fair Value Measurements (Details 3-Reported) $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($) notes_receivable	Dec. 31, 2018 USD ($)
Estimate of Fair Value Measurement [Member]
Financial assets
Current assets(a)	$ 762	$ 13
Other noncurrent assets	135	76
Total financial assets	897	89
Financial liabilities
Other current liabilities	32	37
Long-term debt, including current portion(a)	5,976	5,469
Deferred credits and other liabilities	110	93
Total financial liabilities	6,118	5,599
Reported Value Measurement [Member]
Financial assets
Current assets(a)	761	13
Other noncurrent assets	137	81
Total financial assets	898	94
Financial liabilities
Other current liabilities	43	58
Long-term debt, including current portion(a)	5,526	5,528
Deferred credits and other liabilities	103	88
Total financial liabilities	$ 5,672	$ 5,674
Oil Sands Mining Segment [Member] | Discontinued Operations, Disposed of by Sale [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Number of notes receivable | notes_receivable	2