LONG-TERM OBLIGATIONS - Letters of credit outstanding (Details) - Continuing Operations - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Letters of credit outstanding	$ 82.5	$ 80.1
Credit Agreement 2017
Debt Instrument [Line Items]
Letters of credit outstanding	0.0	0.0
Additional Credit Agreement 2017
Debt Instrument [Line Items]
Letters of credit outstanding	35.3	34.8
Bilateral Arrangements
Debt Instrument [Line Items]
Letters of credit outstanding	$ 47.2	$ 45.3