CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Net Income (Loss) Attributable to Parent	$ 49,569	$ 9,996	$ 293,804	$ 81,699
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract]
Net unrealized gain (loss) from pension and postretirement plans, net of tax	1,608	1,090	6,379	7,890
Other comprehensive income (loss)	1,608	1,090	6,379	7,890
Comprehensive Income (Loss), Net of Tax, Attributable to Parent, Total	51,177	11,086	300,183	89,589
Subsidiaries [Member]
Net Income (Loss) Attributable to Parent	74,125	33,062	351,959	159,420
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract]
Net unrealized gain (loss) from pension and postretirement plans, net of tax	3,757	3,195	12,674	14,765
Amortization Of Financing Cash Flow Hedge Contracts To Earnings During Period Net Of Tax	97	97	289	289
Other comprehensive income (loss)	3,854	3,292	12,963	15,054
Comprehensive Income (Loss), Net of Tax, Attributable to Parent, Total	$ 77,979	$ 36,354	$ 364,922	$ 174,474