Ventures and Variable Interest Entities (Schedule of Variable Interest Entities) (Details) - USD ($) $ in Millions		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Variable Interest Entity [Line Items]
Cash and cash equivalents		$ 576	$ 638	$ 967	$ 780
Trade receivables - third party and affiliates		986	801
Property, plant and equipment (net of accumulated depreciation - 2017: $90; 2016: $50)		3,762	3,577
Accumulated depreciation		2,584	2,239
Intangible assets, net		301	194
Accumulated amortization		591	524	$ 528
Other assets		338	307
Total assets		9,538	8,357
Trade payables		807	625
Current liabilities		1,559	1,077
Deferred income taxes		211	130
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		19	18
Trade receivables - third party and affiliates		5	4
Property, plant and equipment (net of accumulated depreciation - 2017: $90; 2016: $50)		697	734
Intangible assets, net		25	26
Other assets		6	9
Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Property, plant and equipment (net of accumulated depreciation - 2017: $90; 2016: $50)		53	60
Trade payables		25	53
Current installments of long-term debt		18	10
Long-term debt		76	91
Total liabilities		119	154
Maximum exposure to loss		164	240
Fairway Methanol LLC [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		19	18
Trade receivables - third party and affiliates		9	8
Property, plant and equipment (net of accumulated depreciation - 2017: $90; 2016: $50)		697	734
Accumulated depreciation		90	50
Intangible assets, net		25	26
Accumulated amortization		2	1
Other assets		6	9
Total assets	[1]	756	795
Trade payables		16	15
Current liabilities	[2]	4	2
Long-term debt		5	5
Deferred income taxes		3	2
Total liabilities		$ 28	$ 24

[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.