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Schedule I - Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Notes to parent company financial statements
Cash received (paid) for income taxes, net	$ 5.2	$ 39.7	$ (9.3)
WEC Energy Group
Notes to parent company financial statements
Cash (paid) for interest	(82.5)	(89.6)	(68.8)
Cash received (paid) for income taxes, net	169.9	(62.9)	242.9
WEC Energy Group | Bluewater
Notes to parent company financial statements
Issuance of short-term note receivable	115.0	0.0	0.0
WEC Energy Group | UMERC
Notes to parent company financial statements
Issuance of short-term note receivable	40.5	0.0	0.0
WEC Energy Group | Bostco
Notes to parent company financial statements
Settlement of short-term note payable	4.8	0.0	0.0
WEC Energy Group | Wisvest
Notes to parent company financial statements
Settlement of short-term note payable	$ 0.0	$ 40.0	$ 0.0

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The amount of cash paid during the current period to foreign, federal, state, and local authorities as taxes on income, net of any cash received during the current period as refunds for the overpayment of taxes.

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