Quarterly report pursuant to Section 13 or 15(d)

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Items Measured at Fair Value on Recurring Basis (Details)

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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Items Measured at Fair Value on Recurring Basis (Details) - Fair Value, Measurements, Recurring
$ in Millions
Mar. 31, 2018
USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Deferred Compensation Plan Assets $ 35.3
Deferred Compensation Plan Liability (35.3)
Total 0.0
Quoted Prices in Active Markets for Identical Assets (Level 1)  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Deferred Compensation Plan Assets 35.3
Deferred Compensation Plan Liability 0.0
Total 35.3
Significant Other Observable Inputs (Level 2)  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Deferred Compensation Plan Assets 0.0
Deferred Compensation Plan Liability (35.3)
Total (35.3)
Significant Unobservable Inputs (Level 3)  
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Deferred Compensation Plan Assets 0.0
Deferred Compensation Plan Liability 0.0
Total $ 0.0