FINANCING ARRANGEMENTS (Summary of Financing Arrangements) (Details) - USD ($)	Sep. 30, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Current portion of long-term obligations	$ 7,535,000	$ 4,000,000
Long-term obligations, at par	1,631,581,000	1,639,000,000
Revolving credit facility		0
Unamortized debt issuance costs and premium, net	(15,425,000)	(13,463,000)
Long-term obligations, at carrying value	1,616,156,000	1,625,537,000
Total current and long-term obligations, at carrying value	1,623,691,000	1,629,537,000
Term Loan Agreement
Debt Instrument [Line Items]
Total current and long-term obligations, at carrying value	744,100,000
Secured debt \| Term Loan Agreement
Debt Instrument [Line Items]
Current portion of long-term obligations	7,535,000	4,000,000
Long-term obligations, at par	736,581,000	394,000,000
Unsecured debt \| Senior unsecured notes, at 5.25%, due August 1, 2020 (2020 Notes)
Debt Instrument [Line Items]
Long-term obligations, at par	$ 0	400,000,000
Interest rate	5.25%
Unsecured debt \| Senior unsecured notes, at 5.125%, due June 1, 2021 (2021 Notes)
Debt Instrument [Line Items]
Long-term obligations, at par	$ 845,000,000	845,000,000
Interest rate	5.125%
Line of Credit
Debt Instrument [Line Items]
Revolving credit facility	$ 50,000,000	$ 0

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Amount after unamortized (discount) premium and debt issuance costs of long-term debt classified as noncurrent and excluding amounts to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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