CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Net Income (Loss)	$ 414,345	$ 260,849	$ 182,717
Other comprehensive income (loss):
Net unrealized gain (loss) from pension and postretirement plans, net of tax	2,658	59,005	(2,288)
Other comprehensive income (loss)	2,658	59,005	(2,288)
Comprehensive income (loss)	417,003	319,854	180,429
Subsidiaries [Member]
Net Income (Loss)	490,952	336,063	274,280
Other comprehensive income (loss):
Net unrealized gain (loss) from pension and postretirement plans, net of tax	9,711	67,431	7,136
Amortization of treasury interest rate swaps to earnings, net of tax	386	384	385
Other comprehensive income (loss)	10,097	67,815	7,521
Comprehensive income (loss)	$ 501,049	$ 403,878	$ 281,801