Consolidated Condensed Statements of Cash Flows (Unaudited) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013
Operations:
Net income	$ 20,865	$ 22,846
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	50,489	48,155
Gain on disposition of revenue equipment	(3,360)	(5,124)
Deferred income taxes	(3,795)	4,695
Tax benefits from share-based payment arrangement exercises	141	146
Excess tax benefits from share-based payment arrangement exercises	(97)	(122)
Share-based payment arrangement compensation expense	720	862
Income before income taxes attributable to noncontrolling interest		84
Equity in earnings from affiliate	(453)	(203)
Changes in other current operating items:
Receivables	(3,825)	(7,725)
Prepaid expenses and other	1,793	2,501
Accounts payable and accrued liabilities	(3,450)	(252)
Insurance and claims accruals	(645)	(14)
Net cash provided by operating activities	58,383	65,849
CASH FLOWS USED FOR INVESTING ACTIVITIES:
Decrease in cash and cash equivalents resulting from change to equity method of accounting		(1,924)
Other	(27)	(27)
Net cash used for investing activities	(95,203)	(64,728)
CASH FLOWS PROVIDED BY (USED FOR) FINANCING ACTIVITIES:
Borrowings under credit facility and long-term debt	102,912	77,546
Repayment of borrowings under credit facility and long-term debt	(78,231)	(79,451)
Dividends on common stock	(2,504)	(1,937)
Issuance of common stock from share-based payment arrangement exercises	1,055	282
Excess tax benefits from share-based payment arrangement exercises	97	122
Change in net checks issued in excess of cash balances	28
Noncontrolling interest distributions		(84)
Net cash provided by (used for) financing activities	23,357	(3,522)
NET CHANGE IN CASH AND CASH EQUIVALENTS	(13,463)	(2,401)
CASH AND CASH EQUIVALENTS:
Beginning of period	13,650	3,473
End of period	187	1,072
SUPPLEMENTAL NON-CASH DISCLOSURE:
Change in property and equipment not yet paid for	4,264	6,422
Cash paid for:
Interest	114	69
Income taxes	20,001	13,015
Revenue Equipment [Member]
CASH FLOWS USED FOR INVESTING ACTIVITIES:
Proceeds from disposition of property, plant, and equipment	35,429	35,321
Buildings And Land, Office Equipment And Other [Member]
CASH FLOWS USED FOR INVESTING ACTIVITIES:
Proceeds from disposition of property, plant, and equipment	17	2
Revenue Equipment [Member]
CASH FLOWS USED FOR INVESTING ACTIVITIES:
Additions to property, plant, and equipment	(102,752)	(85,864)
Buildings And Land, Office Equipment And Other [Member]
CASH FLOWS USED FOR INVESTING ACTIVITIES:
Additions to property, plant, and equipment	$ (27,870)	$ (12,236)