Ventures and Variable Interest Entities (Schedule of Variable Interest Entities) (Details) - USD ($) $ in Millions		Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Variable Interest Entity [Line Items]
Cash and cash equivalents		$ 441	$ 439	$ 490	$ 576
Trade receivables - third party and affiliates		1,015	1,017
Property, plant and equipment (net of accumulated depreciation - 2019: $140; 2018: $130)		3,721	3,719
Accumulated depreciation		2,871	2,803
Intangible assets (net of accumulated amortization - 2019: $3; 2018: $3)		332	310
Accumulated amortization		595	595
Other assets		309	290
Total assets		9,574	9,313
Trade payables		699	819
Other liabilities		1,822	1,779
Deferred income taxes		273	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: $140; 2018: $130)		650	659
Intangible assets (net of accumulated amortization - 2019: $3; 2018: $3)		23	23
Other assets		4	5
Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Property, plant and equipment (net of accumulated depreciation - 2019: $140; 2018: $130)		39	42
Trade payables		23	27
Long-term debt		54	57
Total liabilities		92	98
Current installments of long-term debt		15	14
Maximum exposure to loss		125	133
Fairway Methanol LLC [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		23	24
Trade receivables - third party and affiliates		10	11
Property, plant and equipment (net of accumulated depreciation - 2019: $140; 2018: $130)		650	659
Accumulated depreciation		141	130
Intangible assets (net of accumulated amortization - 2019: $3; 2018: $3)		23	23
Accumulated amortization		4	3
Other assets		4	5
Total assets	[1]	710	722
Trade payables		8	16
Other liabilities	[2]	7	4
Long-term debt		4	5
Deferred income taxes		3	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.