Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Purchase of common stock	$ (11,184)	$ (63,570)	$ (10,345)
Withholding taxes paid for conversion of employee stock awards	2,914	2,300	1,310
OPERATING ACTIVITIES:
Net earnings (loss) from continuing operations	21,740	21,060	39,155
Net earnings (loss) from discontinued operations	(3,245)	2,428	2,067
Adjustments to reconcile net earnings to net cash provided by operating activities:
Depreciation and amortization	170,751	140,002	125,443
Pension and post-retirement	20,933	11,532	6,920
Deferred income taxes	(30,771)	13,807	23,691
Amortization of stock-based compensation	3,632	3,165	2,454
Amortization of DHL promissory note	0	0	(1,550)
Net (gain) loss on financial instruments	(1,370)	(969)	(920)
Changes in assets and liabilities:
Accounts receivable	(31,313)	(9,597)	(14,410)
Inventory and prepaid supplies	(4,107)	(5,269)	(3,896)
Accounts payable	23,500	5,603	4,424
Unearned revenue	(7,331)	(3,216)	(1,116)
Accrued expenses, salaries, wages, benefits and other liabilities	780	5,678	8,375
Pension and post-retirement assets	(13,083)	(11,819)	(16,098)
Other	3,717	1,611	470
NET CASH PROVIDED BY OPERATING ACTIVITIES	234,992	193,092	175,009
INVESTING ACTIVITIES:
Capital expenditures	(296,939)	(264,477)	(158,714)
Proceeds from property and equipment	381	12,380	6,841
Investment in nonconsolidated affiliate	(11,792)	(17,395)	0
Redemption of long term deposits	9,975	0	0
NET CASH (USED IN) INVESTING ACTIVITIES	(298,375)	(269,492)	(151,873)
FINANCING ACTIVITIES:
Principal payments on long term obligations	(254,446)	(44,069)	(69,344)
Proceeds from borrowings	115,000	185,000	45,000
Proceeds from convertible notes	258,750	0	0
Payments for financing costs	(7,887)	0	0
Purchase convertible note hedges	(56,097)	0	0
NET CASH PROVIDED BY (USED IN) FINANCING ACTIVITIES	79,724	75,061	(35,999)
Proceeds from issuance of warrants	38,502	0	0
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	16,341	(1,339)	(12,863)
CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR	16,358	17,697	30,560
CASH AND CASH EQUIVALENTS AT END OF PERIOD	32,699	16,358	17,697
SUPPLEMENTAL CASH FLOW INFORMATION:
Interest paid, net of amount capitalized	13,693	10,738	10,748
Federal alternative minimum and state income taxes paid	1,938	923	870
SUPPLEMENTAL NON-CASH INFORMATION:
Accrued capital expenditures	25,142	9,118	7,033
Net (gain) loss on financial instruments	$ (79,789)	$ (18,107)	$ 920