FAIR VALUE OF FINANCIAL ASSETS AND FINANCIAL LIABILITIES, LEVEL THREE INPUTS (Details) (Fair Value, Inputs, Level 3 [Member], Market Approach Valuation Technique [Member], Forward Contracts [Member], USD $) In Thousands, unless otherwise specified	3 Months Ended
	Jun. 30, 2012
Derivative Financial Instruments, Assets [Member] | Natural Gas [Member]
Fair Value Inputs, Assets And Liabilities, Quantitative Information [Line Items]
Assets	$ 2,577
Derivative Financial Instruments, Assets [Member] | Electric [Member]
Fair Value Inputs, Assets And Liabilities, Quantitative Information [Line Items]
Assets	7,357
Derivative Financial Instruments, Liabilities [Member] | Natural Gas [Member]
Fair Value Inputs, Assets And Liabilities, Quantitative Information [Line Items]
Liabilities	2,303
Derivative Financial Instruments, Liabilities [Member] | Electric [Member]
Fair Value Inputs, Assets And Liabilities, Quantitative Information [Line Items]
Liabilities	$ 4,553
Minimum [Member] | Natural Gas [Member]
Fair Value Inputs, Assets And Liabilities, Quantitative Information [Line Items]
Fair Value Inputs, Offered Quotes (in dollars per dt and percent)	(0.79)
Maximum [Member] | Natural Gas [Member]
Fair Value Inputs, Assets And Liabilities, Quantitative Information [Line Items]
Fair Value Inputs, Offered Quotes (in dollars per dt and percent)	3.30
On Peak Season [Member] | Minimum [Member] | Electric [Member]
Fair Value Inputs, Assets And Liabilities, Quantitative Information [Line Items]
Fair Value Inputs, Offered Quotes (in dollars per dt and percent)	0.1901
On Peak Season [Member] | Maximum [Member] | Electric [Member]
Fair Value Inputs, Assets And Liabilities, Quantitative Information [Line Items]
Fair Value Inputs, Offered Quotes (in dollars per dt and percent)	1.0000
Off Peak Season [Member] | Minimum [Member] | Electric [Member]
Fair Value Inputs, Assets And Liabilities, Quantitative Information [Line Items]
Fair Value Inputs, Offered Quotes (in dollars per dt and percent)	0.0000
Off Peak Season [Member] | Maximum [Member] | Electric [Member]
Fair Value Inputs, Assets And Liabilities, Quantitative Information [Line Items]
Fair Value Inputs, Offered Quotes (in dollars per dt and percent)	0.8099