Ventures and Variable Interest Entities (Schedule of Variable Interest Entities) (Details) - USD ($) $ in Millions		Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2017
Variable Interest Entity [Line Items]
Cash and cash equivalents		$ 491	$ 439	$ 708	$ 576
Trade receivables - third party and affiliates		971	1,017
Property, plant and equipment (net of accumulated depreciation - 2019: $151; 2018: $130)		3,642	3,719
Accumulated depreciation		2,828	2,803
Intangible assets (net of accumulated amortization - 2019: $4; 2018: $3)		327	310
Accumulated amortization		605	595
Other assets		320	290
Total assets		9,506	9,313
Trade payables		764	819
Other liabilities		1,408	1,779
Deferred income taxes		265	255
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		23	24
Trade receivables - third party and affiliates		5	6
Property, plant and equipment (net of accumulated depreciation - 2019: $151; 2018: $130)		641	659
Intangible assets (net of accumulated amortization - 2019: $4; 2018: $3)		23	23
Other assets		3	5
Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Property, plant and equipment (net of accumulated depreciation - 2019: $151; 2018: $130)		37	42
Trade payables		28	27
Long-term debt		50	58
Total liabilities		93	99
Current installments of long-term debt		15	14
Maximum exposure to loss		124	134
Fairway Methanol LLC [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		29	24
Trade receivables - third party and affiliates		10	11
Property, plant and equipment (net of accumulated depreciation - 2019: $151; 2018: $130)		641	659
Accumulated depreciation		151	130
Intangible assets (net of accumulated amortization - 2019: $4; 2018: $3)		23	23
Accumulated amortization		4	3
Other assets		3	5
Total assets	[1]	706	722
Trade payables		11	16
Other liabilities	[2]	3	4
Long-term debt		4	5
Deferred income taxes		4	3
Total liabilities		$ 22	$ 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.