Derivative and Hedging Instruments (Details-4) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Current and Long-Term Regulatory Asset [Member]
Change in Derivative Fair Value [Roll Forward]
Beginning balance	$ 26,875	$ 31,830
Unrealized gain	(4,895)	(5,493)
Realized (loss) gain reclassified to a deferred account	(2,232)	(1,896)
Realized (loss) gain reclassified to income statement	(5,759)	2,434
Ending balance	13,989	26,875
Other Current Assets [Member]
Change in Derivative Fair Value [Roll Forward]
Beginning balance	1,100	377
Unrealized gain	0	0
Realized (loss) gain reclassified to a deferred account	2,232	1,896
Realized (loss) gain reclassified to income statement	(2,170)	(1,173)
Ending balance	$ 1,162	$ 1,100