Note 3. Segment Reporting Segment Reporting (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Segment Reporting Information [Line Items]
Revenue from external customers	$ 1,427,314	$ 1,492,349	$ 2,799,745	$ 2,861,192
Revenue from internal customers	58,335	64,667	117,452	123,161
Operating income (loss)	84,006	102,700	135,933	135,762
Freight [Member]
Segment Reporting Information [Line Items]
Revenue from external customers	907,809	927,942	1,754,443	1,764,271
Revenue from internal customers	9,097	12,561	18,075	24,259
Operating income (loss)	69,516	83,021	106,892	101,586
Logistics [Member]
Segment Reporting Information [Line Items]
Revenue from external customers	385,885	413,830	784,064	803,202
Revenue from internal customers	20,051	19,820	38,942	36,813
Operating income (loss)	8,004	6,418	16,620	12,592
Truckload [Member]
Segment Reporting Information [Line Items]
Revenue from external customers	132,070	148,930	257,837	289,527
Revenue from internal customers	10,678	15,134	23,636	30,547
Operating income (loss)	9,313	13,499	16,874	19,879
Corporate and Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from external customers	1,550	1,647	3,401	4,192
Revenue from internal customers	18,509	17,152	36,799	31,542
Operating income (loss)	$ (2,827)	$ (238)	$ (4,453)	$ 1,705