SCHEDULE I - CONDENSED PARENT COMPANY FINANCIAL STATEMENTS SHORT-TERM NOTES PAYABLE - RELATED PARTIES (Details) (Integrys Energy Group, Inc., USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
SHORT-TERM NOTES PAYABLE - RELATED PARTIES
Short-term notes payable to related parties	$ 165.7	$ 258.0
PELLC
SHORT-TERM NOTES PAYABLE - RELATED PARTIES
Short-term notes payable to related parties	165.7	201.6
Integrys Energy Services
SHORT-TERM NOTES PAYABLE - RELATED PARTIES
Short-term notes payable to related parties	0	49.4
IBS
SHORT-TERM NOTES PAYABLE - RELATED PARTIES
Short-term notes payable to related parties	$ 0	$ 7.0