PROPERTY, PLANT, AND EQUIPMENT (Details) - USD ($) $ in Millions	9 Months Ended
Sep. 30, 2019	Dec. 31, 2018
Property, plant, and equipment
Net book value of plant classified as a regulatory asset	$ 4,036.2	$ 3,855.8
Cost of removal reserve classified as a regulatory liability	4,248.2	$ 4,288.4
Presque Isle power plant
Property, plant, and equipment
Plant to be retired, at carrying value	164.6
Net book value of plant classified as a regulatory asset	176.3
Cost of removal reserve classified as a regulatory liability	11.7
Wisconsin
Changes to severance liability
Severance liability, balance at beginning of period	15.7
Severance payments	(7.2)
Other	(3.1)
Severance liability, balance at end of period	$ 5.4

Amount of cash payments made as the result of exit or disposal activities. Excludes payments associated with a discontinued operation or an asset retirement obligation.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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The amount for the individual regulatory asset as itemized in a table of regulatory assets as of the end of the period.

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The amount for the individual regulatory liability as itemized in a table of regulatory liabilities as of the end of the period.

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Carrying amount (including both current and noncurrent portions of the accrual) as of the balance sheet date pertaining to a specified type of cost associated with exit from or disposal of business activities or restructuring pursuant to a duly authorized plan.

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This is the value of Property, plant, and equipment, at carrying value which is made up of the net book value of the property, plant, and equipment less the cost of removal reserve.

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