Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012		Dec. 31, 2011
Current assets:
Cash and cash equivalents	$ 5,589		$ 5,450
Trade accounts receivable, net	466,011		411,479
Inventories	23,065		20,932
Prepaid licenses and permits	17,632		16,735
Prepaid insurance	32,474		29,649
Deferred income taxes			5,136
Other current assets	9,761		24,161
Total current assets	554,532		513,542
Property and equipment, at cost:
Revenue and service equipment	2,571,083		2,344,600
Land	36,482		29,246
Structures and improvements	135,974		132,202
Furniture and office equipment	161,167		152,095
Total property and equipment	2,904,706		2,658,143
Less accumulated depreciation	1,019,232		931,273
Net property and equipment	1,885,474		1,726,870
Other assets	24,635		26,920
Total assets	2,464,641	[1]	2,267,332	[1]
Current liabilities:
Current portion of long-term debt	100,000		50,000
Trade accounts payable	266,722		251,625
Claims accruals	47,442		42,364
Accrued payroll	70,647		77,107
Other accrued expenses	17,199		17,419
Deferred income taxes	750
Total current liabilities	502,760		438,515
Long-term debt	585,347		699,177
Other long-term liabilities	53,050		45,382
Deferred income taxes	531,624		516,715
Total liabilities	1,672,781		1,699,789
Commitments and contingencies (Note 9)
Stockholders’ equity:
Preferred stock, $100 par value. 10 million shares authorized; none outstanding
Common stock, $.01 par value. 1 billion shares authorized; (167,099,432 shares issued at December 31, 2012 and 2011, of which 117,529,307 shares and 116,932,448 shares were outstanding at December 31, 2012 and 2011, respectively)	1,671		1,671
Additional paid-in capital	207,073		192,470
Retained earnings	1,985,213		1,758,290
Treasury stock, at cost (49,570,125 shares at December 31, 2012, and 50,166,984 shares at December 31, 2011)	(1,402,097)		(1,384,888)
Total stockholders’ equity	791,860		567,543
Total liabilities and stockholders' equity	$ 2,464,641		$ 2,267,332

[1] Business segment assets exclude the net impact of intercompany transactions and accounts.