Derivative and Hedging Instruments (Details-3) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Derivative collateral required to be posted for ten-year PPA [Abstract]
Minimum collateral required	$ 20,000,000		$ 20,000,000
Maximum collateral required	40,000,000		40,000,000
Commodity Contract [Member] | Regulated Gas Revenues [Member]
Realized losses (gains) on income statement [Line Items]
Realized losses (gains) on income statement	0	0	0	0
Commodity Contract [Member] | Fuel For Electric Generation Purchased Power [Member]
Realized losses (gains) on income statement [Line Items]
Realized losses (gains) on income statement	90,000	484,000	28,000	1,703,000
Commodity Contract [Member] | Cost Of Gas Sold [Member]
Realized losses (gains) on income statement [Line Items]
Realized losses (gains) on income statement	0	(20,000)	1,315,000	610,000
Financial Transmission Rights [Member] | Regulated Gas Revenues [Member]
Realized losses (gains) on income statement [Line Items]
Realized losses (gains) on income statement	0	0	0	0
Financial Transmission Rights [Member] | Fuel For Electric Generation Purchased Power [Member]
Realized losses (gains) on income statement [Line Items]
Realized losses (gains) on income statement	(625,000)	134,000	(371,000)	(135,000)
Financial Transmission Rights [Member] | Cost Of Gas Sold [Member]
Realized losses (gains) on income statement [Line Items]
Realized losses (gains) on income statement	0	0	0	0
Purchased Power Agreement [Member] | Regulated Gas Revenues [Member]
Realized losses (gains) on income statement [Line Items]
Realized losses (gains) on income statement	0	0	0	0
Purchased Power Agreement [Member] | Fuel For Electric Generation Purchased Power [Member]
Realized losses (gains) on income statement [Line Items]
Realized losses (gains) on income statement	0	0	0	0
Purchased Power Agreement [Member] | Cost Of Gas Sold [Member]
Realized losses (gains) on income statement [Line Items]
Realized losses (gains) on income statement	$ 0	$ 0	$ 0	$ 0