DERIVATIVE INSTRUMENTS (Details)	Sep. 30, 2011
Natural Gas (in MMdts) [Member] | Derivative Transaction Type, Purchase [Member]
Derivative [Line Items]
Outstanding derivative contracts notional amount	17.0
Natural Gas (in MMdts) [Member] | Derivative Transaction Type, Sale [Member]
Derivative [Line Items]
Outstanding derivative contracts notional amount	16.7
Electricity (in MMmwh) [Member] | Derivative Transaction Type, Purchase [Member]
Derivative [Line Items]
Outstanding derivative contracts notional amount	1.3
Electricity (in MMmwh) [Member] | Derivative Transaction Type, Sale [Member]
Derivative [Line Items]
Outstanding derivative contracts notional amount	0.1