Derivative and Hedging Instruments (Details-4) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Current and Long-Term Regulatory Asset [Member]
Change in Derivative Fair Value [Roll Forward]
Beginning balance	$ 72,329	$ 42,356
Change in unrealized loss	(5,069)	37,822
Realized loss reclassified to a deferred account	(823)	(2,857)
Realized gain (loss) reclassified to income statement	(2,544)	(4,992)
Ending balance	63,893	72,329
Other Current Assets [Member]
Change in Derivative Fair Value [Roll Forward]
Beginning balance	574	1,604
Change in unrealized loss	0	0
Realized loss reclassified to a deferred account	823	2,857
Realized gain (loss) reclassified to income statement	(986)	(3,887)
Ending balance	$ 411	$ 574