Derivative and Hedging Instruments (Details-5) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Counterparties in net liability position or default [Abstract]
Net liability position of counterparites (less than $0.1 million as of December 31, 2014, $0 as of December 31, 2013)	$ 100,000	$ 0
Number of counterparties in default	0
Commodity Derivative Contracts [Member] | Fuel For Electric Generation Purchased Power [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Realized losses (gains)	(5,515,000)	(564,000)
Commodity Derivative Contracts [Member] | Cost Of Gas Sold Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Realized losses (gains)	(1,103,000)	868,000
Financial Transmission Rights [Member] | Fuel For Electric Generation Purchased Power [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Realized losses (gains)	(1,110,000)	(983,000)
Financial Transmission Rights [Member] | Cost Of Gas Sold Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Realized losses (gains)	0	0
Ten-year PPA [Member]
Derivative collateral required to be posted for ten-year PPA [Abstract]
Minimum collateral that may be required to be posted	20,000,000
Maximum collateral that may be required to be posted	40,000,000
Collateral posted	0
Ten-year PPA [Member] | Fuel For Electric Generation Purchased Power [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Realized losses (gains)	1,515,000	4,209,000
Ten-year PPA [Member] | Cost Of Gas Sold Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Realized losses (gains)	$ 0	$ 0