Consolidated Statements of Cash Flows - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating activities:
Net earnings (loss)		$ (141,514)	$ 7,532	$ (26,680)
Adjustments to reconcile net earnings (loss) to net cash (used in) provided by operating activities:
Depreciation and amortization		79,254	68,027	65,743
Deferred income taxes		(28,552)	(59,272)	(2,424)
Gain (loss) on asset dispositions		753	298	(3,350)
Equity in loss (income) of unconsolidated affiliate		(188)	385	(151)
Impairment of assets		109,024	368	407
Inventory valuation reserves		2,230	2,410	5,179
Changes in operating assets and liabilities:
Accounts receivable	[1]	3,788	(28,329)	(351)
Inventories of spare parts	[1]	4,328	(6,793)	(5,064)
Income taxes receivable	[1]	320	186	220
Other assets	[1]	(21,105)	(9,050)	(14,837)
Accounts payable and accrued liabilities	[1]	16,812	5,754	(19,111)
Other long-term liabilities	[1]	(7,502)	(619)	(142)
Net cash (used in) provided by operating activities	[1]	17,648	(19,103)	(564)
Investing activities:
Purchase of property and equipment		(43,176)	(56,757)	(81,842)
Proceeds from asset dispositions		14,245	1,296	14,983
Purchase of short-term investments		(284,481)	(637,980)	(321,453)
Proceeds from sale of short-term investments		334,488	862,942	316,543
Payments of deposits on aircraft		0	0	(2,249)
Loan to unconsolidated affiliate		(274)	0	(1,200)
Loan to third party		0	(824)	0
Business acquisitions net of cash acquired		0	(126,644)	0
Net cash provided by (used in) investing activities		20,802	42,033	(75,218)
Financing activities:
Debt Issuance costs		(874)	0	0
Repurchase of common stock		(106)	(256)	(529)
Proceeds from line of credit		34,295	152,150	264,700
Payments on line of credit		(151,795)	(168,650)	(188,200)
Proceeds from related party term loan		130,000	0	0
Net cash provided by (used in) financing activities		11,520	(16,756)	75,971
Effect of exchange rate changes on cash and cash equivalents		(176)	0	0
Increase (decrease) in cash, cash equivalents and restricted cash		49,794	6,174	189
Cash, cash equivalents and restricted cash at beginning of period		8,770	2,596	2,407
Cash, cash equivalents and restricted cash at end of period		58,564	8,770	2,596
Cash paid during the period for:
Interest		30,828	30,517	29,169
Income Taxes		2,273	1,231	2,637
Accrued payables related to purchases of property and equipment		$ 52	$ 42	$ 29

[1] Net of the effect of business acquisitions.