COMMON EQUITY - STOCK OPTIONS (Details) - Stock options - USD ($) $ / shares in Units, $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Options Activity
Outstanding, shares, beginning balance	72,698	71,015
Granted, shares		21,638	21,265	23,300
Exercised, shares		(19,955)	0	0
Outstanding, shares, ending balance		72,698	71,015
Options - Weighted Average Exercise Price
Outstanding, Weighted-Average Exercise Price, Beginning	$ 63.41	$ 59.70
Granted, Weighted-Average Exercise Price		68.18
Exercised, Weighted-Average Exercise Price		55.36
Outstanding, Weighted-Average Exercise Price, Ending		$ 63.41	$ 59.70
Options - Additional Disclosures
Outstanding, Weighted-Average Remaining Contractual Life (Years)		7 years 10 months 24 days
Outstanding, Aggregate Intrinsic Value		$ 2.1
Exercisable, shares		8,165
Exercisable, Weighted-Average Exercise Price		$ 57.99
Exercisable, Weighted-Average Remaining Contractual Life (Years)		6 years 8 months 12 days
Exercisable, Aggregate Intrinsic Value		$ 0.3
Intrinsic value of options exercised		0.5
Tax benefit from option exercises		0.1
Compensation cost not yet recognized		$ 0.4
Weighted-average period over which unrecognized compensation cost is expected to be recognized		1 year 7 months 6 days
Estimated weighted-average fair value per stock option (in dollars per share)		$ 8.60	$ 7.68	$ 7.53
Subsequent event
Options Activity
Granted, shares	22,042
Options - Weighted Average Exercise Price
Granted, Weighted-Average Exercise Price	$ 91.49
Options - Additional Disclosures
Estimated weighted-average fair value per stock option (in dollars per share)	$ 10.82
WEC Energy Group
Options - Additional Disclosures
Cash received by WEC Energy Group from options exercised by WPS employees		$ 1.1