Consolidated Condensed Statements of Cash Flows (Unaudited) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
Operations:
Net income	$ 19,548	$ 16,622
Adjustments to reconcile net income to net cash flows from operating activities:
Depreciation	45,114	42,358
Gain on disposition of revenue equipment	(4,053)	(2,819)
Deferred income taxes	3,723	8,043
Tax benefits from share-based payment arrangement exercises	350	164
Excess tax benefits from share-based payment arrangement exercises	(282)	(142)
Share-based payment arrangement compensation expense	1,047	930
Income before income taxes attributable to noncontrolling interest	467	708
Changes in other current operating items:
Receivables	(10,764)	(3,473)
Prepaid expenses and other	2,240	712
Accounts payable and accrued liabilities	5,114	365
Insurance and claims accruals	285	(2,724)
Net cash provided by operating activities	62,789	60,744
CASH FLOWS USED FOR INVESTING ACTIVITIES:
Other	(27)	111
Net cash used for investing activities	(77,606)	(24,072)
CASH FLOWS USED FOR FINANCING ACTIVITIES:
Borrowings under credit facility and long-term debt	14,216	35,382
Repayment of borrowings under credit facility and long-term debt	(14,216)	(54,728)
Dividends on common stock	(1,545)	(1,318)
Issuance of common stock from share-based payment arrangement exercises	616	137
Excess tax benefits from share-based payment arrangement exercises	282	142
Noncontrolling interest distributions	(230)	(13)
Change in net checks issued in excess of cash balances		(1,066)
Net cash used for financing activities	(877)	(21,464)
NET CHANGE IN CASH AND CASH EQUIVALENTS	(15,694)	15,208
CASH AND CASH EQUIVALENTS:
Beginning of period	20,821	5,306
End of period	5,127	20,514
Cash paid (received) for:
Interest	6	32
Income taxes	6,723	(6,477)
Non-cash investing activities:
Change in property and equipment not yet paid for	2,325	5,323
Revenue Equipment [Member]
CASH FLOWS USED FOR INVESTING ACTIVITIES:
Additions to property, plant, and equipment	(107,904)	(45,321)
Buildings And Land, Office Equipment And Other [Member]
CASH FLOWS USED FOR INVESTING ACTIVITIES:
Additions to property, plant, and equipment	(11,750)	(7,116)
Revenue Equipment [Member]
CASH FLOWS USED FOR INVESTING ACTIVITIES:
Proceeds from disposition of property, plant, and equipment	41,521	28,181
Buildings And Land, Office Equipment And Other [Member]
CASH FLOWS USED FOR INVESTING ACTIVITIES:
Proceeds from disposition of property, plant, and equipment	$ 554	$ 73