FAIR VALUE MEASUREMENTS - Carrying Value And Fair Value Of Financial Instruments Disclosure (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total long-term debt	$ 5,368	$ 5,424
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total long-term debt	6,266	6,065
Senior Notes | Carrying Value | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total long-term debt	3,548	3,802
Senior Notes | Fair Value | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total long-term debt	4,446	4,446
Industrial Revenue Bonds | Carrying Value | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total long-term debt	94	94
Industrial Revenue Bonds | Fair Value | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total long-term debt	94	91
Line of Credit | Carrying Value | Level 2 | ABL Facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total long-term debt	1,670	1,510
Line of Credit | Carrying Value | Level 2 | EDC Revolving Facilities - outstanding balance
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total long-term debt	56	18
Line of Credit | Fair Value | Level 2 | ABL Facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total long-term debt	1,670	1,510
Line of Credit | Fair Value | Level 2 | EDC Revolving Facilities - outstanding balance
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total long-term debt	$ 56	$ 18