Fair Value of Financial Instruments (Details-3) (USD $) In Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Changes in level 3 assets and liabilities measured at fair value on a recurring basis [Abstract]
Beginning balance,	$ (22,148)	$ (19,662)	$ (19,216)	$ (13,047)
Realized and unrealized gains (losses):
Included in regulatory liabilities (assets)	(835)	2,058	(3,767)	(4,557)
Included in other comprehensive income	0	0	0	0
Included in earnings	579	(435)	564	(1,101)
Included in current assets	(229)	0	(229)	0
Purchases	334	0	334	0
Sales	0	0	71	101
Issuances	0	0	0	0
Settlements	(684)	435	(740)	1,000
Transfers in or out of level 3	0	0	0	0
Balance as of June 30,	(22,983)	(17,604)	(22,983)	(17,604)
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.	579	(435)	564	(1,101)
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 [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.	579	(435)	564	(1,076)
Cost Of Gas Sold [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	$ (25)

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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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