Derivative and Hedging Instruments (Details-4) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Regulatory Asset [Member]
Change In Derivative Fair Value [Roll Forward]
Beginning balance,	$ 63,893	$ 72,329
Change in unrealized gain	(13,601)	(1,697)
Realized loss reclassified to a deferred account	1,535	(290)
Realized gain (loss) on income statement	6,386	(1,145)
Ending balance,	58,213	69,197
Other Current Assets [Member]
Change In Derivative Fair Value [Roll Forward]
Beginning balance,	411	574
Change in unrealized gain	0	0
Realized loss reclassified to a deferred account	(1,535)	290
Realized gain (loss) on income statement	1,475	(605)
Ending balance,	$ 351	$ 259