RISK MANAGMENT ACTIVITIES - UTILITY SEGMENTS, NOTIONAL VOLUMES (Details) (Non-hedge derivatives, Utility segments)	12 Months Ended
	Dec. 31, 2014 MMBTU	Dec. 31, 2013 MMBTU
Natural gas contracts | Purchases
Risk management activities
Notional volume of outstanding derivative contracts (mmbtu or kwh)	186,000,000	312,480,000
Natural gas contracts | Sales
Risk management activities
Notional volume of outstanding derivative contracts (mmbtu or kwh)	0	2,930,000
FTRs | Other transactions
Risk management activities
Notional volume of outstanding derivative contracts (mmbtu or kwh)	4,287,700,000	3,427,000,000
Petroleum product contracts | Purchases
Risk management activities
Notional volume of outstanding derivative contracts (barrels)	100,000	100,000
Petroleum product contracts | Sales
Risk management activities
Notional volume of outstanding derivative contracts (barrels)	0	0
Coal contracts | Purchases
Risk management activities
Notional volume of outstanding derivative contracts (tons)	3,000,000	4,800,000
Coal contracts | Sales
Risk management activities
Notional volume of outstanding derivative contracts (tons)	0	0