(Goodwill acquired in business combination by reportable segment) (Details) (USD $) In Thousands, unless otherwise specified				12 Months Ended															12 Months Ended															12 Months Ended															12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2011 Morgan Southern	Dec. 31, 2011 Bruenger	Dec. 31, 2011 James Brooks	Dec. 31, 2011 Prime	Dec. 31, 2012 CTL	Dec. 31, 2012 D&E	Dec. 31, 2012 CTW	Dec. 31, 2012 R&M	Dec. 31, 2012 EFS	Dec. 31, 2012 Central Cal	Dec. 31, 2012 A&A	Dec. 31, 2012 DCT	Dec. 31, 2012 LTL	Dec. 31, 2011 LTL	Dec. 31, 2010 LTL	Dec. 31, 2011 LTL Morgan Southern	Dec. 31, 2011 LTL Bruenger	Dec. 31, 2011 LTL James Brooks	Dec. 31, 2011 LTL Prime	Dec. 31, 2012 LTL CTL	Dec. 31, 2012 LTL D&E	Dec. 31, 2012 LTL CTW	Dec. 31, 2012 LTL R&M	Dec. 31, 2012 LTL EFS	Dec. 31, 2012 LTL Central Cal	Dec. 31, 2012 LTL A&A	Dec. 31, 2012 LTL DCT	Dec. 31, 2012 TL	Dec. 31, 2011 TL	Dec. 31, 2010 TL	Dec. 31, 2011 TL Morgan Southern	Dec. 31, 2011 TL Bruenger	Dec. 31, 2011 TL James Brooks	Dec. 31, 2011 TL Prime	Dec. 31, 2012 TL CTL	Dec. 31, 2012 TL D&E	Dec. 31, 2012 TL CTW	Dec. 31, 2012 TL R&M	Dec. 31, 2012 TL EFS	Dec. 31, 2012 TL Central Cal	Dec. 31, 2012 TL A&A	Dec. 31, 2012 TL DCT	Dec. 31, 2012 TMS	Dec. 31, 2011 TMS	Dec. 31, 2010 TMS	Dec. 31, 2011 TMS Morgan Southern	Dec. 31, 2011 TMS Bruenger	Dec. 31, 2011 TMS James Brooks	Dec. 31, 2011 TMS Prime	Dec. 31, 2012 TMS CTL	Dec. 31, 2012 TMS D&E	Dec. 31, 2012 TMS CTW	Dec. 31, 2012 TMS R&M	Dec. 31, 2012 TMS EFS	Dec. 31, 2012 TMS Central Cal	Dec. 31, 2012 TMS A&A	Dec. 31, 2012 TMS DCT
Rollforward of goodwill by reportable segment
Goodwill beginning balance	$ 442,143	$ 364,687	$ 246,888													$ 197,456	$ 185,406	$ 185,406													$ 202,547	$ 143,575	$ 25,776													$ 42,140	$ 35,706	$ 35,706
Acquisition during the year				15,019	4,182	7,944	90,654	6,434	8,211	9,223	20,164	12,050	6,688	12,361	2,325				0	0	0	0	0	0	0	0	12,050	0	0	0				15,019	4,182	7,944	90,654	0	8,211	9,223	20,164	0	6,688	12,361	2,325				0	0	0	0	6,434	0	0	0	0	0	0	0
Goodwill closing balance	$ 442,143	$ 364,687	$ 246,888													$ 197,456	$ 185,406	$ 185,406													$ 202,547	$ 143,575	$ 25,776													$ 42,140	$ 35,706	$ 35,706