Ventures and Variable Interest Entities (Schedule of Variable Interest Entities) (Details) - USD ($) $ in Millions		Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Variable Interest Entity [Line Items]
Cash and cash equivalents		$ 703	$ 576	$ 461	$ 638
Trade receivables - third party and affiliates		1,086	986
Property, plant and equipment (net of accumulated depreciation - 2018: $120; 2017: $90)		3,699	3,762
Accumulated depreciation		2,739	2,584
Intangible assets (net of accumulated amortization - 2018: $3; 2017: $2)		317	301
Accumulated amortization		593	591
Other assets		413	338
Total assets		9,824	9,538
Trade payables		819	807
Other liabilities		1,532	1,559
Deferred income taxes		246	211
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		27	19
Trade receivables - third party and affiliates		5	5
Property, plant and equipment (net of accumulated depreciation - 2018: $120; 2017: $90)		668	697
Intangible assets (net of accumulated amortization - 2018: $3; 2017: $2)		23	25
Other assets		4	6
Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Property, plant and equipment (net of accumulated depreciation - 2018: $120; 2017: $90)		46	53
Trade payables		29	25
Long-term debt		62	76
Total liabilities		104	119
Current installments of long-term debt		13	18
Maximum exposure to loss		141	164
Fairway Methanol LLC [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		27	19
Trade receivables - third party and affiliates		10	9
Property, plant and equipment (net of accumulated depreciation - 2018: $120; 2017: $90)		668	697
Accumulated depreciation		120	90
Intangible assets (net of accumulated amortization - 2018: $3; 2017: $2)		23	25
Accumulated amortization		3	2
Other assets		4	6
Total assets	[1]	732	756
Trade payables		13	16
Other liabilities	[2]	4	4
Long-term debt		5	5
Deferred income taxes		3	3
Total liabilities		$ 25	$ 28

[1] Assets can only be used to settle the obligations of Fairway.

[2] Primarily represents amounts owed by Fairway to the Company for reimbursement of expenditures.