Accounting for Derivative Instruments and Hedging Activities Recognized in Other Comprehensive Income (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Parent Company [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Cash Flow Hedge Loss to be Reclassified within Twelve Months			$ (500,000)
Subsidiaries [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Cash Flow Hedge Loss to be Reclassified within Twelve Months			(2,000,000)
Cash Flow Hedging [Member] | Parent Company [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	0	(1,325,000)	(678,000)	(2,475,000)
Cash Flow Hedging [Member] | Parent Company [Member] | Electric generation fuel [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	0	0	0	0
Cash Flow Hedging [Member] | Subsidiaries [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(122,000)	(122,000)	(1,348,000)	(3,030,000)
Cash Flow Hedging [Member] | Subsidiaries [Member] | Electric generation fuel [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	$ 0	$ 0	$ 0	$ 0