REGULATORY ASSETS AND LIABILITIES - REGULATORY LIABILITIES (Details) - USD ($) $ in Millions	Jun. 30, 2023	Dec. 31, 2022
Regulatory liabilities
Other current liabilities	$ 107.5	$ 56.4
Regulatory liabilities	3,712.9	3,735.5
Total regulatory liabilities	3,820.4	3,791.9
Income tax related items
Regulatory liabilities
Total regulatory liabilities	1,934.0	1,956.6
Removal costs
Regulatory liabilities
Total regulatory liabilities	1,292.7	1,260.9
Pension and OPEB benefits
Regulatory liabilities
Total regulatory liabilities	331.6	340.5
Energy costs refundable through rate adjustments
Regulatory liabilities
Total regulatory liabilities	106.1	53.4
Derivatives
Regulatory liabilities
Total regulatory liabilities	40.6	76.7
Uncollectible expense
Regulatory liabilities
Total regulatory liabilities	24.4	24.0
Decoupling
Regulatory liabilities
Total regulatory liabilities	16.7	20.2
Energy efficiency programs
Regulatory liabilities
Total regulatory liabilities	13.5	10.4
Other, net
Regulatory liabilities
Total regulatory liabilities	$ 60.8	$ 49.2