RISK MANAGEMENT ACTIVITIES - INTEGRYS ENERGY SERVICES SEGMENT, NOTIONAL VOLUMES (Details) (Non-hedge derivatives, Integrys Energy Services)	6 Months Ended	12 Months Ended
	Jun. 30, 2014 MMBTU	Dec. 31, 2013 MMBTU
Natural gas contracts | Purchases
Risk management activities
Notional volume of outstanding derivative contracts (mmbtu or kwh)	116,460,000	119,990,000
Natural gas contracts | Sales
Risk management activities
Notional volume of outstanding derivative contracts (mmbtu or kwh)	126,250,000	106,540,000
Electric contracts | Purchases
Risk management activities
Notional volume of outstanding derivative contracts (mmbtu or kwh)	40,031,900,000	49,186,300,000
Electric contracts | Sales
Risk management activities
Notional volume of outstanding derivative contracts (mmbtu or kwh)	23,508,900,000	30,813,800,000