CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Income Statement [Abstract]
Operating revenues, net	$ 195,543	$ 160,554	$ 374,511	$ 298,605
Expenses:
Direct expenses	159,494	134,088	307,697	252,790
Selling, general and administrative expenses	10,024	9,672	18,290	18,508
Total operating expenses	169,518	143,760	325,987	271,298
Gain on disposal of assets	(14,701)	(679)	(14,676)	(690)
Impairment of assets	421		421
Equity in loss of unconsolidated affiliate	596		1,083
Operating income	39,709	17,473	61,696	27,997
Interest expense	7,257	7,440	14,666	14,640
Other income, net	(73)	(57)	(225)	(363)
Total expenses	7,184	7,383	14,441	14,277
Earnings before income taxes	32,525	10,090	47,255	13,720
Income tax expense	13,009	4,036	18,901	5,488
Net earnings	$ 19,516	$ 6,054	$ 28,354	$ 8,232
Weighted average shares outstanding:
Basic	15,474	15,312	15,474	15,312
Diluted	15,674	15,550	15,673	15,486
Net earnings per share:
Basic	$ 1.26	$ 0.40	$ 1.83	$ 0.54
Diluted	$ 1.25	$ 0.39	$ 1.81	$ 0.53