SHORT-TERM DEBT AND LINES OF CREDIT - CREDIT FACILITIES (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020 USD ($) extension	Dec. 31, 2019 USD ($)
Short-term borrowings
Available capacity under existing agreements	$ 188.2
Number of extensions available on a credit facility | extension	2
Length of credit facility extension	1 year
Letters of credit
Short-term borrowings
Letters of credit issued inside credit facility	$ 1.3
Commercial paper
Short-term borrowings
Short-term borrowings outstanding	210.5	$ 91.5
Credit facility maturing October 2022
Short-term borrowings
Total short-term credit capacity	$ 400.0