INVESTMENT IN TRANSMISSION AFFILIATES - RECEIVABLES AND PAYABLES (Details) - USD ($) $ in Millions	Jun. 30, 2023	Dec. 31, 2022
Investment in transmission affiliates
Accounts payable for services received from ATC	$ 748.5	$ 1,198.1
ATC
Investment in transmission affiliates
Accounts receivable for services provided to ATC	1.5	1.2
Accounts payable for services received from ATC	31.7	30.4
Amounts due from ATC for transmission infrastructure upgrades (1)	$ 45.9	$ 26.6

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