Investment in ATC and ATC Holdco (Details-2) - ATC [Member] - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Schedule of Equity Method Investments [Line Items]
Operating revenues	$ 191,605	$ 185,900	$ 382,604	$ 374,594
Operating expenses	(95,256)	(92,384)	(190,747)	(187,488)
Other income, net	344	663	748	1,041
Interest expense, net	(29,059)	(28,792)	(57,499)	(57,663)
Earnings before members' income taxes	$ 67,634	$ 65,387	$ 135,106	$ 130,484