Segment Reporting (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013 Segment	Jun. 30, 2012	Dec. 31, 2012
Segment Reporting Information [Line Items]
Number of Operating Segments			3
Schedule of financial data of reportable segments
Revenues	$ 331,908	$ 262,546	$ 631,288	$ 499,119
Operating Income	24,398	18,573	43,535	33,213
Interest expense	1,610	2,071	3,485	3,918
Income before provision for income taxes	22,788	16,502	40,050	29,295
Depreciation and amortization	3,846	2,125	7,201	4,085
Payments to Acquire Productive Assets, Non Cash and Cash	9,502	3,553	18,945	6,812
Total assets	761,748		761,748		700,808
LTL [Member]
Schedule of financial data of reportable segments
Revenues	146,545	129,717	279,236	248,670
Operating Income	11,808	10,454	20,786	18,904
Depreciation and amortization	1,004	546	1,782	1,061
Payments to Acquire Productive Assets, Non Cash and Cash	837	1,272	1,960	3,859
Total assets	519,771		519,771		490,067
TL [Member]
Schedule of financial data of reportable segments
Revenues	161,235	111,045	307,776	209,072
Operating Income	11,351	6,829	21,019	12,491
Depreciation and amortization	2,617	1,385	5,014	2,644
Payments to Acquire Productive Assets, Non Cash and Cash	8,231	2,252	16,180	2,896
Total assets	376,133		376,133		339,890
TMS [Member]
Schedule of financial data of reportable segments
Revenues	26,967	23,127	48,410	43,807
Operating Income	3,966	2,765	6,289	4,977
Depreciation and amortization	189	194	352	380
Payments to Acquire Productive Assets, Non Cash and Cash	28	29	52	57
Total assets	74,549		74,549		61,076
Eliminations [Member]
Schedule of financial data of reportable segments
Revenues	(2,839)	(1,343)	(4,134)	(2,430)
Total assets	(208,705)		(208,705)		(190,225)
Corporate [Member]
Schedule of financial data of reportable segments
Operating Income	(2,727)	(1,475)	(4,559)	(3,159)
Depreciation and amortization	36	0	53	0
Payments to Acquire Productive Assets, Non Cash and Cash	$ 406	$ 0	$ 753	$ 0