SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES CASH AND CASH EQUIVALENTS (Details)	12 Months Ended
Dec. 31, 2018
Cash and cash equivalents
Maximum term of original maturity to classify instrument as cash equivalents	3 months

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

No definition available.

Name:	wps_MaximumTermOfOriginalMaturityToClassifyInstrumentAsCashEquivalent
Namespace Prefix:	wps_
Data Type:	us-types:durationStringItemType
Balance Type:	na
Period Type:	duration