SUPPLEMENTAL GUARANTOR FINANCIAL INFORMATION (Cash Flows) (Details) - USD ($) $ in Millions	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018
Supplemental Guarantor Financial Information Statements Of Cash Flows [Line Items]
Net Cash Provided by (Used in) Operating Activities	$ 236.1	$ 264.3
Capital expenditures	(191.3)	(176.0)
Proceeds from disposition of property, plant and equipment	0.0	0.1
Proceeds from disposition of non-consolidated affiliate	20.0	0.0
Net investing activities	(171.3)	(175.9)
Long-term debt:
Borrowings	25.0	570.0
Repayments	(50.6)	(650.1)
Common stock repurchased and retired	(26.7)	(9.1)
Stock options exercised	1.5	2.2
Dividends paid	(65.7)	(66.9)
Debt issuance costs	0.0	(8.5)
Intercompany financing activities	0.0	0.0
Net financing activities	(116.5)	(162.4)
Effect of exchange rate changes on cash and cash equivalents	(0.2)	(0.2)
Net (decrease) increase in cash and cash equivalents	(51.9)	(74.2)
Cash and cash equivalents, end of period	126.9	144.2
Cash and cash equivalents, beginning of period	178.8	218.4
Parent Guarantor
Supplemental Guarantor Financial Information Statements Of Cash Flows [Line Items]
Net Cash Provided by (Used in) Operating Activities	120.1	157.2
Capital expenditures	(86.9)	(72.3)
Proceeds from disposition of property, plant and equipment		0.0
Proceeds from disposition of non-consolidated affiliate	20.0	95.0
Net investing activities	(66.9)	22.7
Long-term debt:
Borrowings	0.0	550.0
Repayments	(0.6)	(20.4)
Common stock repurchased and retired	(26.7)	(9.1)
Stock options exercised	1.5	2.2
Dividends paid	(65.7)	(66.9)
Debt issuance costs		(8.5)
Intercompany financing activities	(50.0)	(610.0)
Net financing activities	(141.5)	(162.7)
Effect of exchange rate changes on cash and cash equivalents	0.0	0.0
Net (decrease) increase in cash and cash equivalents	(88.3)	17.2
Cash and cash equivalents, end of period	3.7	74.3
Cash and cash equivalents, beginning of period	92.0	57.1
Issuer
Supplemental Guarantor Financial Information Statements Of Cash Flows [Line Items]
Net Cash Provided by (Used in) Operating Activities	0.0	0.0
Capital expenditures	0.0	0.0
Proceeds from disposition of property, plant and equipment		0.0
Proceeds from disposition of non-consolidated affiliate	0.0	95.0
Net investing activities	0.0	95.0
Long-term debt:
Borrowings	0.0	0.0
Repayments	(50.0)	(610.0)
Common stock repurchased and retired	0.0	0.0
Stock options exercised	0.0	0.0
Dividends paid	0.0	(95.0)
Debt issuance costs		0.0
Intercompany financing activities	50.0	610.0
Net financing activities	0.0	(95.0)
Effect of exchange rate changes on cash and cash equivalents	0.0	0.0
Net (decrease) increase in cash and cash equivalents	0.0	0.0
Cash and cash equivalents, end of period	0.0	0.0
Cash and cash equivalents, beginning of period	0.0	0.0
Subsidiary Non-Guarantor
Supplemental Guarantor Financial Information Statements Of Cash Flows [Line Items]
Net Cash Provided by (Used in) Operating Activities	116.0	107.1
Capital expenditures	(104.4)	(103.7)
Proceeds from disposition of property, plant and equipment		0.1
Proceeds from disposition of non-consolidated affiliate	0.0	0.0
Net investing activities	(104.4)	(103.6)
Long-term debt:
Borrowings	25.0	20.0
Repayments	0.0	(19.7)
Common stock repurchased and retired	0.0	0.0
Stock options exercised	0.0	0.0
Dividends paid	0.0	(95.0)
Debt issuance costs		0.0
Intercompany financing activities	0.0	0.0
Net financing activities	25.0	(94.7)
Effect of exchange rate changes on cash and cash equivalents	(0.2)	(0.2)
Net (decrease) increase in cash and cash equivalents	36.4	(91.4)
Cash and cash equivalents, end of period	123.2	69.9
Cash and cash equivalents, beginning of period	86.8	161.3
Eliminations
Supplemental Guarantor Financial Information Statements Of Cash Flows [Line Items]
Net Cash Provided by (Used in) Operating Activities	0.0	0.0
Capital expenditures	0.0	0.0
Proceeds from disposition of property, plant and equipment		0.0
Proceeds from disposition of non-consolidated affiliate	0.0	(190.0)
Net investing activities	0.0	(190.0)
Long-term debt:
Borrowings	0.0	0.0
Repayments	0.0	0.0
Common stock repurchased and retired	0.0	0.0
Stock options exercised	0.0	0.0
Dividends paid	0.0	190.0
Debt issuance costs		0.0
Intercompany financing activities	0.0	0.0
Net financing activities	0.0	190.0
Effect of exchange rate changes on cash and cash equivalents	0.0	0.0
Net (decrease) increase in cash and cash equivalents	0.0	0.0
Cash and cash equivalents, end of period	0.0	0.0
Cash and cash equivalents, beginning of period	$ 0.0	$ 0.0

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[Line Items] for Supplemental Guarantor Financial Information Statements Of Cash Flows

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Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.

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Amount of increase (decrease) in cash and cash equivalents. Cash and cash equivalents are the amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Includes effect from exchange rate changes.

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