SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES EMPLOYEE BENEFITS (Details)	12 Months Ended
Dec. 31, 2014
Employee benefits
Recognition period for transition obligation related to other postretirement benefit plans that existed prior to the merger	20 years
Recognition period for changes in realized and unrealized investment gains and losses	5 years
IBS
Employee benefits
Recognition period for differences between actual investment returns and expected return on plan assets	5 years

Represents the period of recognition of differences between actual investment returns and the expected return on plan assets of the defined benefit plan.

No definition available.

Name:	wps_DefinedBenefitPlanDifferencesBetweenActualInvestmentReturnsAndExpectedReturnOnPlanAssetsRecognitionPeriod
Namespace Prefix:	wps_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration