CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Operating activities:
Net earnings	$ 42,131	$ 14,616
Adjustments to reconcile net earnings to net cash provided by operating activities:
Depreciation and amortization	31,424	25,536
Deferred income taxes	26,158	10,566
Equity in loss of unconsolidated affiliate	911
(Gain) loss on asset dispositions	(16,075)	11
Impairment of assets	421
Other	655	3,725
Changes in operating assets and liabilities	(17,520)	(28,418)
Net cash provided by operating activities	68,105	26,036
Investing activities:
Purchase of property and equipment	(86,092)	(83,187)
Proceeds from asset dispositions	39,822	9,702
Purchase of short-term investments	(314,519)	(167,952)
Proceeds from sale of short-term investments	287,043	194,957
Deposits returned on aircraft	6,908	5,369
Deposits paid on aircraft	(2,693)	(11,176)
Net cash used in investing activities	(69,531)	(52,287)
Financing activities:
Proceeds from line of credit	101,273	91,863
Payments on line of credit	(99,763)	(68,915)
Repurchase of common stock for payroll tax withholding requirements	(1,037)
Net cash provided by financing activities	473	22,948
Decrease in cash	(953)	(3,303)
Cash, beginning of period	2,849	5,091
Cash, end of period	1,896	1,788
Cash paid during the period for:
Interest	15,112	15,078
Income taxes	229	563
Noncash investing activities:
Other current liabilities and accrued payables related to purchase of property and equipment	$ 102	$ 330