CREDIT LOSSES - GROSS RECEIVABLES AND RELATED ALLOWANCES (Details) - USD ($) $ in Millions	Sep. 30, 2020	Jun. 30, 2020	Dec. 31, 2019
Utility segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable and unbilled revenues	$ 195.6
Allowance for credit losses	14.7	$ 10.0	$ 4.2
Accounts receivable and unbilled revenues, net	180.9
Total accounts receivable, net - past due greater than 90 days	$ 11.1
Past due greater than 90 days - collection risk mitigated by regulatory mechanisms	93.40%
Amount of net accounts receivable with regulatory protections	$ 66.3
Percent of net accounts receivable with regulatory protections	36.70%
Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable and unbilled revenues	$ 0.0