LONG-TERM OBLIGATIONS - Schedule of Letters of Credit Outstanding (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Letters of credit outstanding, amount	$ 76.7	$ 80.1
$400 Million Facility
Debt Instrument [Line Items]
Letters of credit outstanding, amount	0.0	0.0
$300 Million Facility
Debt Instrument [Line Items]
Letters of credit outstanding, amount	34.9	34.8
Bilateral Arrangements
Debt Instrument [Line Items]
Letters of credit outstanding, amount	$ 41.8	$ 45.3