Note 3. Segment Reporting Segment Reporting (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Segment Reporting Information [Line Items]
Revenue from external customers	$ 1,492,349	$ 1,381,370	$ 2,861,192	$ 2,717,534
Revenue from internal customers	64,667	61,008	123,161	118,343
Operating Income (Loss)	102,700	76,299	135,762	107,898
Freight [Member]
Segment Reporting Information [Line Items]
Revenue from external customers	927,942	881,824	1,764,271	1,698,960
Revenue from internal customers	12,561	10,451	24,259	20,851
Operating Income (Loss)	83,021	54,689	101,586	70,713
Logistics [Member]
Segment Reporting Information [Line Items]
Revenue from external customers	413,830	353,528	803,202	732,256
Revenue from internal customers	19,820	16,850	36,813	30,479
Operating Income (Loss)	6,418	6,039	12,592	12,571
Truckload [Member]
Segment Reporting Information [Line Items]
Revenue from external customers	148,930	144,490	289,527	282,839
Revenue from internal customers	15,134	17,314	30,547	35,968
Operating Income (Loss)	13,499	10,873	19,879	20,828
Corporate and Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from external customers	1,647	1,528	4,192	3,479
Revenue from internal customers	17,152	16,393	31,542	31,045
Operating Income (Loss)	$ (238)	$ 4,698	$ 1,705	$ 3,786