Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Write off of Deferred Debt Issuance Cost	$ 17,445	$ 10,468	$ 3,135
Purchase of common stock	0	(3,581)	(11,184)
Withholding taxes paid for conversion of employee stock awards	2,438	2,325	2,914
OPERATING ACTIVITIES:
Net earnings from continuing operations	59,983	67,883	21,740
Net earnings (loss) from discontinued operations	1,219	1,402	(3,245)
Adjustments to reconcile net earnings to net cash provided by operating activities:
Depreciation and amortization	285,353	204,559	170,751
Pension and post-retirement	15,700	3,766	20,933
Deferred income taxes	10,478	18,986	(30,771)
Amortization of stock-based compensation	7,002	5,047	3,632
Net (gain) loss on financial instruments	10,000	8	(1,400)
Changes in assets and liabilities:
Accounts receivable	(14,551)	25,380	(31,313)
Inventory and prepaid supplies	(6,493)	(3,273)	(4,107)
Accounts payable	3,340	10,724	23,500
Unearned revenue	1,446	(3,824)	(7,331)
Accrued expenses, salaries, wages, benefits and other liabilities	13,390	3,605	780
Pension and post-retirement assets	(12,132)	(35,293)	(13,083)
Other	2,456	(4,109)	582
NET CASH PROVIDED BY OPERATING ACTIVITIES	396,938	298,025	234,992
INVESTING ACTIVITIES:
Expenditures for property and equipment	(453,502)	(292,915)	(296,939)
Proceeds from property and equipment	10,804	17,570	381
Investment in nonconsolidated affiliate	(24,360)	(866,558)	(11,792)
Redemption of long term deposits	0	0	9,975
NET CASH (USED IN) INVESTING ACTIVITIES	(467,058)	(1,141,903)	(298,375)
FINANCING ACTIVITIES:
Principal payments on long term obligations	(39,500)	(58,640)	(254,446)
Proceeds from borrowings	100,018	945,000	115,000
Proceeds from convertible notes	0	0	258,750
Payments for financing costs	(1,081)	(9,953)	(7,887)
Purchase convertible note hedges	0	0	(56,097)
NET CASH PROVIDED BY FINANCING ACTIVITIES	56,999	870,501	79,724
Proceeds from issuance of warrants	0	0	38,502
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	(13,121)	26,623	16,341
CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR	59,322	32,699	16,358
CASH AND CASH EQUIVALENTS AT END OF YEAR	46,201	59,322	32,699
SUPPLEMENTAL CASH FLOW INFORMATION:
Interest paid, net of amount capitalized	57,546	17,278	13,693
Federal alternative minimum and state income taxes paid	1,294	1,213	1,938
SUPPLEMENTAL NON-CASH INFORMATION:
Accrued expenditures for property and equipment	38,396	11,234	25,142
Net (gain) loss on financial instruments	(12,302)	7,296	(79,789)
Accrued consideration for acquisition	$ 0	$ 7,845	$ 0