Derivative and Hedging Instruments (Details-3) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Derivative collateral required to be posted for ten-year PPA [Abstract]
Minimum collateral required	$ 20,000,000
Maximum collateral required	40,000,000
Commodity Derivative Contracts [Member] | Regulated Gas Revenues [Member]
Realized losses (gains) on income statement [Line Items]
Realized losses (gains) on income statement	0	0
Commodity Derivative Contracts [Member] | Fuel For Electric Generation Purchased Power [Member]
Realized losses (gains) on income statement [Line Items]
Realized losses (gains) on income statement	(258,000)	2,570,000
Commodity Derivative Contracts [Member] | Cost Of Gas Sold Expense [Member]
Realized losses (gains) on income statement [Line Items]
Realized losses (gains) on income statement	2,194,000	1,652,000
Financial Transmission Rights [Member] | Regulated Gas Revenues [Member]
Realized losses (gains) on income statement [Line Items]
Realized losses (gains) on income statement	0	0
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	(267,000)	(136,000)
Financial Transmission Rights [Member] | Cost Of Gas Sold Expense [Member]
Realized losses (gains) on income statement [Line Items]
Realized losses (gains) on income statement	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
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
Purchased Power Agreement [Member] | Cost Of Gas Sold Expense [Member]
Realized losses (gains) on income statement [Line Items]
Realized losses (gains) on income statement	$ 0	$ 0