Note 3. Segment Reporting Segment Reporting (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Segment Reporting Information [Line Items]
Revenue from external customers	$ 1,372,431	$ 1,368,843
Revenue from internal customers	59,117	58,494
Operating income (loss)	51,927	33,062
Freight [Member]
Segment Reporting Information [Line Items]
Revenue from external customers	846,634	836,329
Revenue from internal customers	8,978	11,698
Operating income (loss)	37,376	18,565
Logistics [Member]
Segment Reporting Information [Line Items]
Revenue from external customers	398,179	389,372
Revenue from internal customers	18,891	16,993
Operating income (loss)	8,616	6,174
Truckload [Member]
Segment Reporting Information [Line Items]
Revenue from external customers	125,767	140,597
Revenue from internal customers	12,958	15,413
Operating income (loss)	7,561	6,380
Corporate and Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from external customers	1,851	2,545
Revenue from internal customers	18,290	14,390
Operating income (loss)	$ (1,626)	$ 1,943