Fair Value of Financial Instruments (Details-3) (USD $) In Thousands, unless otherwise specified	3 Months Ended	9 Months Ended
Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Changes in level 3 assets and liabilities measured at fair value on a recurring basis [Abstract]
Beginning balance,	$ (79,580)	$ (22,983)	$ (40,661)	$ (19,216)
Realized and unrealized gains (losses):
Included in regulatory liabilities (assets)	3,465	(2,927)	(35,455)	(6,694)
Included in other comprehensive income	0	0	0	0
Included in earnings	(3,422)	182	(6,659)	815
Included in current assets	0	(7)	(77)	(66)
Purchases	5,864	178	7,764	342
Sales	45	0	77	0
Issuances	0	0	0	0
Settlements	(2,487)	(353)	(1,104)	(1,091)
Transfers in or out of level 3	0	0	0	0
Ending balance,	(76,115)	(25,910)	(76,115)	(25,910)
Total gains (losses) included in earnings attributed to the change in unrealized gains (losses) related to assets and liabilities	0	0	0	0
Realized and unrealized gains (losses) included in income for level 3 instruments [Line Items]
Realized and unrealized gains (losses) included in income for level 3 instruments.	(3,422)	182	(6,659)	815
Regulated Gas Revenues [Member]
Realized and unrealized gains (losses) included in income for level 3 instruments [Line Items]
Realized and unrealized gains (losses) included in income for level 3 instruments.	0	0	0	0
Purchased Power Expense [Member]
Realized and unrealized gains (losses) included in income for level 3 instruments [Line Items]
Realized and unrealized gains (losses) included in income for level 3 instruments.	(3,422)	182	(6,659)	815
Cost Of Gas Sold Expense [Member]
Realized and unrealized gains (losses) included in income for level 3 instruments [Line Items]
Realized and unrealized gains (losses) included in income for level 3 instruments.	$ 0	$ 0	$ 0	$ 0

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This item represents the amount of the total realized and unrealized gains or losses for the period which are included in the statement of income (or changes in net assets); the fair value of which assets and liabilities was or is measured on a recurring basis using significant unobservable inputs (Level 3).

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Issues that have taken place during the period in relation to assets measured at fair value and categorized within Level 3 of the fair value hierarchy.

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Purchases that have taken place during the period in relation to assets measured at fair value and categorized within Level 3 of the fair value hierarchy.

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This element represents an asset measured at fair value using significant unobservable inputs (Level 3) which is required for reconciliation purposes of beginning and ending balances.

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