FINANCIAL INSTRUMENTS - Fair Value - Narrative (Details) - Drop Down Assets 2016 Acquisition - USD ($) $ in Millions	Mar. 31, 2020	Mar. 03, 2016	Jun. 30, 2020	Feb. 26, 2019
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Payments to Acquire Businesses, Gross		$ 360.0
Remaining cash consideration payable			$ 303.5	$ 303.5
Scenario Forecast
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Annual accrued Interest rate on unpaid consideration	8.00%
Scenario Forecast | Minimum
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Minimum remaining consideration to be paid percentage			50.00%