CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Net Income (loss)	$ (23,233)	$ (32,952)	$ 71,703	$ 99,202
Other comprehensive income(loss):
Net unrealized gain (loss) from pension and postretirement plans, net of tax	1,630	91	6,800	183
Other comprehensive income (loss)	1,630	91	6,800	183
Comprehensive income (loss)	(21,603)	(32,861)	78,503	99,385
Amortization of right-of-use asset	152	124	304	282
Interest on lease liabilities	9	10	19	19
FInance Lease, Cost	161	134	323	301
Operating lease cost	5,669	5,223	11,149	10,007
Net unrealized gain (loss) from pension and postretirement plans, net of tax	433	25	1,806	50
Subsidiaries [Member]
Net Income (loss)	15,037	(8,325)	126,358	138,977
Other comprehensive income(loss):
Net unrealized gain (loss) from pension and postretirement plans, net of tax	3,860	2,512	11,570	5,022
Amortization Of Financing Cash Flow Hedge Contracts To Earnings During Period Net Of Tax	96	96	192	192
Other comprehensive income (loss)	3,956	2,608	11,762	5,214
Comprehensive income (loss)	18,993	(5,717)	138,120	144,191
Amortization of Financing Cash Flow Hedge Contracts to Earnings Tax	25	26	51	51
Net unrealized gain (loss) from pension and postretirement plans, net of tax	$ 1,025	$ 667	$ 3,072	$ 1,335