Schedule I - Income Statements (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income statements
Equity (loss) from equity method investment									$ 127.6	$ 136.7	$ 154.3
Other income, net									102.2	70.3	73.7
Interest expense									501.5	445.1	415.7
Income before income taxes									1,259.7	1,230.3	1,588.4
Income tax benefit									(125.0)	(169.8)	(383.5)
Net income attributed to common shareholders	$ 243.9	$ 234.3	$ 235.7	$ 420.1	$ 205.0	$ 233.2	$ 231.0	$ 390.1	1,134.0	1,059.3	1,203.7
WEC Energy Group
Income statements
Operating expenses									4.7	5.0	6.0
Equity (loss) from equity method investment									1,210.5	1,108.3	1,234.7
Other income, net									6.3	6.8	2.1
Interest expense									122.3	104.1	82.0
Income before income taxes									1,089.8	1,006.0	1,148.8
Income tax benefit									44.2	53.3	54.9
Net income attributed to common shareholders									$ 1,134.0	$ 1,059.3	$ 1,203.7