SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - RECENTLY ISSUED ACCOUNTING PRONOUNCEMENTS (NARRATIVE) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Jan. 01, 2020	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2018	Jan. 01, 2018	Jan. 01, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Decrease in retained earnings			$ (535.7)	$ (193.5)	$ (196.6)	$ (576.7)	$ (650.1)
Total right of use assets			66.5
Present value of lease liabilities			$ 72.5
Reclassification of stranded income tax effects from the Tax Cuts and Jobs Act	$ 0.0
Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total right of use assets				72.0
Present value of lease liabilities				$ 72.0
Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassification of stranded income tax effects from the Tax Cuts and Jobs Act	(205.4)
Accumulated other comprehensive income
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassification of stranded income tax effects from the Tax Cuts and Jobs Act	$ 205.4
Subsequent Event | Accounting Standards Update 2016-13
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Decrease in retained earnings		$ 18.0