RISK MANAGEMENT ACTIVITIES - NONREGULATED SEGMENTS, NOTIONAL VOLUMES (Details) (Non-hedge derivatives, Nonregulated segments)	3 Months Ended	12 Months Ended
	Mar. 31, 2014 Btu	Dec. 31, 2013 Btu
Natural gas contracts | Purchases
Risk management activities
Notional volume of outstanding derivative contracts (therms or kwh)	919,200,000	1,199,900,000
Natural gas contracts | Sales
Risk management activities
Notional volume of outstanding derivative contracts (therms or kwh)	774,300,000	1,065,400,000
Electric contracts | Purchases
Risk management activities
Notional volume of outstanding derivative contracts (therms or kwh)	40,473,700,000	49,186,300,000
Electric contracts | Sales
Risk management activities
Notional volume of outstanding derivative contracts (therms or kwh)	25,245,000,000	30,813,800,000