Derivative and Hedging Instruments (Details-4) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Regulatory Asset [Member]
Change In Derivative Fair Value [Roll Forward]
Beginning balance,	$ 48,853	$ 66,649	$ 63,893	$ 72,329
Change in unrealized loss (gain)	5,329	2,330	(18,090)	(1,330)
Realized gain (loss) reclassified to a deferred account	(314)	(275)	1,120	(953)
Realized gain (loss) reclassified to income statement	(1,184)	(621)	5,761	(1,963)
Ending balance,	52,684	68,083	52,684	68,083
Other Current Assets [Member]
Change In Derivative Fair Value [Roll Forward]
Beginning balance,	676	658	411	574
Change in unrealized loss (gain)	0	0	0	0
Realized gain (loss) reclassified to a deferred account	314	275	(1,120)	953
Realized gain (loss) reclassified to income statement	(249)	(111)	1,450	(705)
Ending balance,	$ 741	$ 822	$ 741	$ 822