CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Income Statement [Abstract]
Operating revenues, net	$ 200,762	$ 170,857	$ 575,273	$ 469,462
Expenses:
Direct expenses	160,731	141,706	468,428	394,496
Selling, general and administrative expenses	9,785	9,784	28,075	28,292
Total operating expenses	170,516	151,490	496,503	422,788
(Gain) loss on disposal of assets, net	(1,399)	701	(16,075)	11
Impairment of assets			421
Equity in (income) loss of unconsolidated affiliate	(172)		911
Operating income	31,817	18,666	93,513	46,663
Interest expense	7,768	7,488	22,434	22,128
Other income, net	(163)	(262)	(388)	(625)
Total expenses	7,605	7,226	22,046	21,503
Earnings before income taxes	24,212	11,440	71,467	25,160
Income tax expense	10,435	5,056	29,336	10,544
Net earnings	$ 13,777	$ 6,384	$ 42,131	$ 14,616
Weighted average shares outstanding:
Basic	15,474	15,312	15,474	15,312
Diluted	15,639	15,522	15,617	15,481
Net earnings per share:
Basic	$ 0.89	$ 0.42	$ 2.72	$ 0.96
Diluted	$ 0.88	$ 0.41	$ 2.70	$ 0.94