Related Parties - Other Transactions (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
Jun. 30, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Related parties
Proceeds from assets transferred to affiliates		$ 0.1	$ 8.8	$ 0.0
Proceeds from liabilities transferred from WBS			10.0
Payments for assets transferred from WBS			59.8
We Power LLC
Related parties
Lease payments paid to related party		393.2	373.7	420.5
Construction work in progress billed to related party		35.1	39.5	57.3
WBS
Related parties
Charges to related party for services and billings		102.6	61.5	255.7
Charges from related party for services and billings		205.3	243.4	215.4
WPS
Related parties
Charges to related party for services and billings		13.2	17.8	28.2
Charges from related party for services and billings		9.3	10.9	4.5
Natural gas purchases		2.0	1.9	1.6
WG
Related parties
Charges to related party for services and billings		41.1	59.0	64.0
Charges from related party for services and billings		30.1	32.6	23.1
Natural gas purchases		5.4	5.3	5.3
Proceeds from assets transferred to affiliates		5.3
UMERC
Related parties
Charges to related party for services and billings		10.5	15.8	125.5
Electric sales to UMERC		7.9	29.6	30.8
Bluewater
Related parties
Charges to related party for services and billings		14.2	15.0	2.7
Natural gas purchases		2.3	0.0	0.0
ATC
Related parties
Charges to related party for services and billings		14.9	13.9	10.9
Charges from related party for services and billings		230.6	232.0	241.4
Refund from ATC related to a FERC audit		0.0	15.4	0.0
Refund from ATC per FERC ROE order		$ 0.0	$ 0.0	$ 19.4
Bluewater
Related parties
Purchase price	$ 226.0

Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer.

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Expenses recognized resulting from transactions (excluding transactions that are eliminated in consolidated or combined financial statements) with related party.

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Purchases during the period (excluding transactions that are eliminated in consolidated or combined financial statements) with related party.

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The amount of construction work in progress billed to W.E. Power, LLC, a subsidiary of WEC Energy Group, Inc., for Port Washington Generating Station Units 1 and 2 and Oak Creek expansion Units 1 and 2.

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The amount of the refund received from ATC due to a FERC audit.

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The amount of lease payments made to W.E. Power, LLC, a subsidiary of WEC Energy Group, Inc., for Port Washington Generating Station Units 1 and 2 and Oak Creek expansion Units 1 and 2.

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Payments made for the transfer of assets from a related party.

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Proceeds from assets transferred to related party.

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Proceeds from (payments for) the transfer of liabilities from (to) a related party.

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Refund of previous year's revenue that wasn't distributed by ATC. This resulted from an order by the FERC.

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Charges to related parties for services, construction, and/or operations (excluding transactions that are eliminated in consolidated or combined financial statements) during the period.

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