Note 3. Segment Reporting Segment Reporting (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Segment Reporting Information [Line Items]
Revenue from External Customers	$ 1,504,150	$ 1,398,021	$ 4,365,342	$ 4,115,555
Revenue from Internal Customers	65,526	64,471	188,687	182,814
Operating Income (Loss)	91,375	67,675	227,137	175,573
Freight [Member]
Segment Reporting Information [Line Items]
Revenue from External Customers	934,313	888,508	2,698,584	2,587,468
Revenue from Internal Customers	11,993	10,746	36,252	31,597
Operating Income (Loss)	71,889	51,570	173,475	122,283
Logistics [Member]
Segment Reporting Information [Line Items]
Revenue from External Customers	422,645	362,830	1,225,847	1,095,086
Revenue from Internal Customers	21,300	17,719	58,113	48,198
Operating Income (Loss)	7,602	8,178	20,194	20,749
Truckload [Member]
Segment Reporting Information [Line Items]
Revenue from External Customers	145,320	144,583	434,847	427,422
Revenue from Internal Customers	13,866	17,596	44,413	53,564
Operating Income (Loss)	10,694	8,971	30,573	29,799
Corporate and Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from External Customers	1,872	2,100	6,064	5,579
Revenue from Internal Customers	18,367	18,410	49,909	49,455
Operating Income (Loss)	$ 1,190	$ (1,044)	$ 2,895	$ 2,742