SIGNIFICANT ACCOUNTING POLICIES - INCOME TAXES (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
SIGNIFICANT ACCOUNTING POLICIES
Tax Act, income tax expense (benefit)	$ (0.2)		$ 3.1
Remeasurement and discrete adjustments related to the Tax Act		$ (2.9)
Sequestration rate (as a percent)			6.20%