REGULATORY MATTERS Changes in Regulatory Assets and Liabilities (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013
Revenue Accruals and Deferrals
Beginning balance	$ (72,168)
Net refund of 2011 revenue deferrals and accruals, including accrued interest	35,296
Net revenue deferral for the nine months ended September 30, 2013	(63,628)
Net accrued interest payable for the nine months ended September 30, 2013	(2,037)
Ending balance	$ (102,537)