Unaudited Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Dec. 31, 2018
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	$ 615	$ 463	$ 497	$ 439
Current Assets
Accounts Receivable, Allowance for Credit Loss, Current	10	9
Trade receivables - third party and affiliates	716	850
Nontrade Receivables, Current	347	331
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment	3,201	2,957
Property, plant and equipment (net of accumulated depreciation - 2020: $3,201; 2019: $2,957; variable interest entity restricted - 2020: $602; 2019: $622)	3,851	3,713
Other assets	412	338
Intangible assets (variable interest entity restricted - 2020: $21; 2019: $22)	$ 317	$ 312
Stockholders' Equity
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	100,000,000	100,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Treasury stock, shares	52,143,916	49,417,965
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	400,000,000	400,000,000
Common stock, shares issued	169,373,705	168,973,172
Common stock, shares outstanding	117,229,789	119,555,207
Variable Interest Entity, Primary Beneficiary [Member]
Current Assets
Trade receivables - third party and affiliates	$ 6	$ 6