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FAIR VALUE MEASUREMENTS - Carrying Value And Fair Value Of Financial Instruments Disclosure (Details) - USD ($) $ in Millions | Jun. 30, 2020 | Dec. 31, 2019
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Carrying Value [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Total long-term debt, fair value | $ 4,451.6 | $ 2,113.8
Fair Value [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Total long-term debt, fair value | 4,317.8 | 2,237.0
Senior Notes [Member] | Carrying Value [Member] | Fair Value, Inputs, Level 1 [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Total long-term debt, fair value | 3,807.3 | 2,113.8
Senior Notes [Member] | Fair Value [Member] | Fair Value, Inputs, Level 1 [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Total long-term debt, fair value | 3,681.8 | 2,237.0
Industrial Revenue Bonds [Member] | Carrying Value [Member] | Fair Value, Inputs, Level 1 [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Total long-term debt, fair value | 94.3 | 0.0
Industrial Revenue Bonds [Member] | Fair Value [Member] | Fair Value, Inputs, Level 1 [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Total long-term debt, fair value | 86.0 | 0.0
Line of Credit [Member] | Carrying Value [Member] | Fair Value, Inputs, Level 2 [Member] | Credit Facility |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Total long-term debt, fair value | 550.0 | 0.0
Line of Credit [Member] | Fair Value [Member] | Fair Value, Inputs, Level 2 [Member] | Credit Facility |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Total long-term debt, fair value | $ 550.0 | $ 0.0

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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- Definition The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. + References No definition available. + Details
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- Details
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- Details
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- Details
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- Details
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- Details
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- Details
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