Consolidated Statements of Comprehensive Income (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Operating Revenue	$ 582,257	$ 545,745	$ 528,623
Operating Expenses
Salaries, wages, and benefits	178,736	167,073	166,717
Rent and purchased transportation	12,808	6,273	7,527
Fuel	172,315	168,981	161,915
Operations and maintenance	22,345	25,282	20,938
Operating taxes and licenses	10,516	8,694	9,225
Insurance and claims	14,888	14,906	13,142
Communications and utilities	3,552	2,953	2,957
Depreciation and amortization	68,908	57,158	57,226
Other operating expenses	19,157	14,633	14,552
Gain on disposal of property and equipment	(33,270)	(15,109)	(32,133)
Total operating expenses	469,955	450,844	422,066
Operating income	112,302	94,901	106,557
Interest income	462	674	773
Interest Expense	(208)	0	0
Income before income taxes	112,556	95,575	107,330
Federal and state income taxes	41,974	34,034	37,398
Net income	70,582	61,541	69,932
Other comprehensive income, net of tax	1,284	1,797	0
Comprehensive income	$ 71,866	$ 63,338	$ 69,932
Net income per share
Basic	$ 0.83	$ 0.72	$ 0.78
Diluted	$ 0.83	$ 0.71	$ 0.78
Weighted average shares outstanding
Basic	85,209	85,892	89,656
Diluted	85,441	86,201	89,673
Dividends declared per share	$ 0.08	$ 1.08	$ 0.08