Derivative and Hedging Instruments (Details-4) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Current and Long-Term Regulatory Asset [Member]
Change in Derivative Fair Value [Roll Forward]
Beginning balance	$ 31,830	$ 41,958
Unrealized (gain) loss	(5,493)	(11,094)
Realized (loss) gain reclassified to a deferred account	(1,896)	523
Realized gain (loss) reclassified to income statement	2,434	443
Ending balance	26,875	31,830
Other Current Assets [Member]
Change in Derivative Fair Value [Roll Forward]
Beginning balance	377	806
Unrealized (gain) loss	0	0
Realized (loss) gain reclassified to a deferred account	1,896	(523)
Realized gain (loss) reclassified to income statement	(1,173)	94
Ending balance	$ 1,100	$ 377