Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Withholding taxes paid for conversion of employee stock awards	$ 1,839	$ 1,496
OPERATING ACTIVITIES:
Net earnings from continuing operations	28,571	(3,998)
Net earnings from discontinued operations	4,008	62
Adjustments to reconcile net earnings to net cash provided by operating activities:
Depreciation and amortization	153,088	139,516
Pension and post-retirement	1,944	7,850
Deferred income taxes	6,597	8,021
Amortization of stock-based compensation	3,951	3,394
Net loss on financial instruments	10,200	10,700
Changes in assets and liabilities:
Accounts receivable	(3,677)	21,235
Inventory and prepaid supplies	(6,992)	(4,242)
Accounts payable	9,628	(3,899)
Unearned revenue and grants	26,631	896
Accrued expenses, salaries, wages, benefits and other liabilities	(12,104)	1,874
Pension and post-retirement assets	(10,049)	(4,747)
Other	(3,631)	2,281
NET CASH PROVIDED BY OPERATING ACTIVITIES	248,996	209,443
INVESTING ACTIVITIES:
Expenditures for property and equipment	(265,882)	(216,769)
Proceeds from property and equipment	9,080	78
Investment in nonconsolidated affiliate	(5,556)	(18,429)
NET CASH USED IN INVESTING ACTIVITIES	(262,358)	(235,120)
FINANCING ACTIVITIES:
Principal payments on long term obligations	(543,240)	(15,938)
Proceeds from borrowings	80,000	40,000
Proceeds from bond issuance	500,000	0
Payments for financing costs	(7,507)	(1,081)
NET CASH PROVIDED BY FINANCING ACTIVITIES	27,414	21,139
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	14,052	(4,538)
CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR	46,201	59,322
CASH AND CASH EQUIVALENTS AT END OF YEAR	60,253	54,784
SUPPLEMENTAL CASH FLOW INFORMATION:
Interest paid, net of amount capitalized	16,779	30,338
Federal alternative minimum and state income taxes paid	650	533
SUPPLEMENTAL NON-CASH INFORMATION:
Accrued expenditures for property and equipment	44,171	26,601
Net (gain) loss on financial instruments	(2,679)	(31,386)
Net Income (Loss) Attributable to Noncontrolling Interest	9,277	9,814
Asset Impairment Charges	39,075	0
Proceeds from (Payments for) Other Financing Activities	$ 0	$ (346)