Fair Value of Financial Instruments (Details-3) (USD $) In Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Changes in level 3 assets and liabilities measured at fair value on a recurring basis [Abstract]
Beginning balance,	$ (22,983)	$ (17,604)	$ (19,216)	$ (13,047)
Realized and unrealized gains (losses):
Included in regulatory liabilities (assets)	(2,927)	(1,594)	(6,694)	(6,151)
Included in other comprehensive income	0	0	0	0
Included in earnings	182	(306)	815	(1,409)
Included in current assets	(7)	0	(66)	0
Purchases	178	0	342	0
Sales	0	122	0	223
Issuances	0	0	0	0
Settlements	(353)	184	(1,091)	1,186
Transfers in or out of level 3	0	0	0	0
Ending balance,	(25,910)	(19,198)	(25,910)	(19,198)
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.	182	(306)	815	(1,409)
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.	182	(311)	815	(1,389)
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	$ 5	$ 0	$ (20)

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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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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Sales 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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Settlements 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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