Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

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Fixed interest rate related to the interest rate derivative.

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The amount of net gains or losses on interest rate cash flow hedges reclassified during the period to earnings from accumulated other comprehensive income upon the hedged transaction affecting earnings.

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The cash inflow from a debt initially having maturity due after one year or beyond the operating cycle, if longer.

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Amount of unrealized gain (loss) related to the increase or decrease in fair value of interest rate derivatives designated as cash flow hedging instruments, which was recorded in accumulated other comprehensive income to the extent that the cash flow hedge was determined to be effective.

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Carrying value as of the balance sheet date of uncollateralized debt obligation (with maturities initially due after one year or beyond the operating cycle if longer), excluding current portion.

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DERIVATIVE INSTRUMENTS - CASH FLOW HEDGES (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2015
Derivative [Line Items]
Issuance of long-term debt			$ 600.0	$ 210.0
Interest rate swaps
Derivative [Line Items]
Amount of net derivative gain recognized in OCI	$ 0.4	$ 0.0	0.4	0.0
Amount of net derivative gain reclassified from accumulated OCI to interest expense	0.2	$ 0.6	1.3	$ 1.7
Amount to be reclassified from accumulated OCI to interest expense	1.6		1.6
WEC Energy Group \| WEC 2007 Junior Notes due 2067
Derivative [Line Items]
Long-term debt outstanding	500.0		500.0
WEC Energy Group \| Total senior note issued in June 2015
Derivative [Line Items]
Issuance of long-term debt					$ 1,200.0
WEC Energy Group \| Interest rate swaps
Derivative [Line Items]
Interest rate swap notional value	$ 250.0		$ 250.0
Interest rate swap fixed interest rate	4.9765%		4.9765%
Amount of net derivative gain recognized in OCI					$ 19.0