Investments (Details-3) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Equity method investment summarized assets [Abstract]
Total Current Assets	$ 199,371	$ 209,519
Total Assets	2,371,906	2,253,651	$ 2,081,664
Equity method investment summarized liabilities and equity [Abstract]
Total Current Liabilities	117,847	190,926
Total Other Credits	612,380	567,422
Total Liabilities and Capitalization	2,371,906	2,253,651
ATC [Member]
Equity method investment summarized income statement [Abstract]
Operating revenues	754,838	758,117	744,371
Operating expenses	(376,153)	(372,463)	(373,527)
Other income, net	1,144	1,922	48
Interest expense, net	(115,089)	(112,818)	(110,490)
Earnings before members' income taxes	264,740	274,758	$ 260,402
Equity method investment summarized assets [Abstract]
Total Current Assets	89,747	92,735
Total Noncurrent Assets	5,628,127	5,400,538
Total Assets	5,717,874	5,493,273
Equity method investment summarized liabilities and equity [Abstract]
Total Current Liabilities	436,918	310,749
Long-term debt	2,513,009	2,512,246
Total Other Credits	421,997	378,205
Total Equity	2,345,950	2,292,073
Total Liabilities and Capitalization	$ 5,717,874	$ 5,493,273