Note 3. Segment Reporting Segment Reporting (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Segment Reporting Information [Line Items]
Revenue from external customers	$ 1,368,843	$ 1,336,164
Revenue from internal customers	58,494	57,335
Operating Income (Loss)	33,062	31,599
Freight [Member]
Segment Reporting Information [Line Items]
Revenue from external customers	836,329	817,136
Revenue from internal customers	11,698	10,400
Operating Income (Loss)	18,565	16,024
Logistics [Member]
Segment Reporting Information [Line Items]
Revenue from external customers	389,372	378,728
Revenue from internal customers	16,993	13,629
Operating Income (Loss)	6,174	6,532
Truckload [Member]
Segment Reporting Information [Line Items]
Revenue from external customers	140,597	138,349
Revenue from internal customers	15,413	18,654
Operating Income (Loss)	6,380	9,955
Corporate and Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from external customers	2,545	1,951
Revenue from internal customers	14,390	14,652
Operating Income (Loss)	$ 1,943	$ (912)