Ventures and Variable Interest Entities (Schedule of Variable Interest Entities) (Details) - USD ($) $ in Millions		Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Variable Interest Entity [Line Items]
Cash and cash equivalents		$ 570	$ 463	$ 441	$ 439
Trade receivables - third party and affiliates		853	850
Non-trade receivables, net		307	331
Property, plant and equipment (net of accumulated depreciation - 2020: $185; 2019: $174)		3,678	3,713
Accumulated depreciation		3,001	2,957
Intangible assets (net of accumulated amortization - 2020: $4; 2019: $4)		302	312
Accumulated amortization		607	612
Other assets		381	338
Total assets		9,545	9,476
Trade payables		724	780
Other liabilities		1,928	1,754
Deferred income taxes		258	257
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		37	57
Trade receivables - third party and affiliates		4	6
Property, plant and equipment (net of accumulated depreciation - 2020: $185; 2019: $174)		619	622
Intangible assets (net of accumulated amortization - 2020: $4; 2019: $4)		22	22
Other assets		17	9
Variable Interest Entity, Primary Beneficiary [Member] | Fairway Methanol LLC [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		37	57
Trade receivables - third party and affiliates		7	12
Non-trade receivables, net		2	0
Property, plant and equipment (net of accumulated depreciation - 2020: $185; 2019: $174)		619	622
Accumulated depreciation		185	174
Intangible assets (net of accumulated amortization - 2020: $4; 2019: $4)		22	22
Accumulated amortization		4	4
Other assets		17	9
Total assets	[1]	704	722
Trade payables		8	24
Other liabilities	[2]	9	5
Long-term debt		3	4
Deferred income taxes		4	4
Total liabilities		24	37
Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Property, plant and equipment (net of accumulated depreciation - 2020: $185; 2019: $174)		28	31
Trade payables		29	30
Long-term debt		36	41
Total liabilities		81	87
Current installments of long-term debt		16	16
Maximum exposure to loss		$ 104	$ 113

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

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