Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Operating activities:
Net (loss) earnings	$ (26,680)	$ 26,924	$ 32,688
Adjustments to reconcile net earnings to net cash provided by operating activities:
Depreciation and amortization	65,743	71,618	50,848
Deferred income taxes	(2,424)	12,894	16,071
(Loss) gain on asset dispositions	(3,350)	339	848
Equity in (profit) loss of unconsolidated affiliate	(151)	306	96
Loss on debt extinguishment			29,833
Impairment of assets	407		10,507
Inventory valuation reserves	5,179	3,231
Other		(1,277)	(96)
Changes in operating assets and liabilities:
Accounts receivable	(351)	36,579	(6,758)
Inventories of spare parts	(5,064)	1,441	(2,656)
Income taxes receivable	220	466	644
Other assets	(14,837)	(14,998)	(1,212)
Accounts payable and accrued liabilities	(19,111)	(3,859)	(10,946)
Other long-term liabilities	(142)	254	(348)
Net cash (used in) provided by operating activities	(564)	133,918	119,519
Investing activities:
Purchase of property and equipment	(81,842)	(57,123)	(157,690)
Proceeds from asset dispositions	14,983	5,236	10,266
Purchase of short-term investments	(321,453)	(608,649)	(465,094)
Proceeds from sale of short-term investments	316,543	505,966	363,110
Payments of deposits on aircraft	(2,249)	(1,273)	(6,948)
Refunds of deposits on aircraft		6,010	11,506
Loan to unconsolidated affiliate	(1,200)		(200)
Net cash used in investing activities	(75,218)	(149,833)	(245,050)
Financing activities:
Proceeds from issuance of Senior Notes due 2019			500,000
Repayment of Senior Notes due 2018			(300,000)
Premium and costs to retire debt early			(26,749)
Debt issuance costs			(6,232)
Repurchase of common stock	(529)	(2,448)	(152)
Proceeds from line of credit	264,700	232,660	264,253
Payments on line of credit	(188,200)	(218,160)	(300,253)
Net cash provided by (used in) financing activities	75,971	12,052	130,867
Increase (decrease) in cash	189	(3,863)	5,336
Cash, beginning of year	2,407	6,270	934
Cash, end of year	2,596	2,407	6,270
Cash paid during the period for:
Interest	29,169	27,657	25,415
Income Taxes	2,637	5,521	9,590
Accrued payables related to purchases of property and equipment	$ 29	$ 1,339	$ 192