Summary of Significant Accounting Policies Cash and Cash Equivalents (Details)	12 Months Ended
Dec. 31, 2019
Accounting Policies [Abstract]
Maximum term of original maturity to classify instrument as cash equivalent	3 months

Maximum term of original maturity to classify an instrument as a cash equivalent.

No definition available.

Name:	wec_MaximumTermOfOriginalMaturityToClassifyInstrumentAsCashEquivalent
Namespace Prefix:	wec_
Data Type:	us-types:durationStringItemType
Balance Type:	na
Period Type:	duration