FINANCIAL STATEMENT PRESENTATION - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Quantifying Misstatement in Current Year Financial Statements, Amount		$ 3,000,000		$ 10,000,000
Electric Wholesale Sales	27,529,000	29,341,000	92,581,000	88,469,000
Utilities Operating Expense, Purchased Power	67,429,000	57,085,000	189,384,000	165,078,000
Total Fuel and Purchased Energy	157,071,000	172,534,000	451,587,000	451,479,000
Total Operating Expenses	307,276,000	327,699,000	903,936,000	904,615,000
Scenario, Previously Reported [Member]
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Electric Wholesale Sales		32,494,000		98,282,000
Utilities Operating Expense, Purchased Power		60,238,000		174,891,000
Total Fuel and Purchased Energy		175,687,000		461,292,000
Total Operating Expenses		$ 330,852,000		$ 914,428,000