Segment Reporting (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014 Segment	Sep. 30, 2013	Dec. 31, 2013
Segment Reporting Information [Line Items]
Number of Operating Segments			3
Schedule of financial data of reportable segments
Revenues	$ 498,086	$ 363,156	$ 1,340,298	$ 994,444
Operating Income	25,280	23,659	71,472	67,194
Interest expense	3,827	2,078	8,936	5,563
Income before provision for income taxes	21,453	21,581	62,536	61,631
Depreciation and amortization	6,319	4,029	16,788	11,230
Capital expenditures, cash and non-cash	9,075	6,030	30,556	24,379
Total assets	1,247,401		1,247,401		871,880
TL [Member]
Schedule of financial data of reportable segments
Revenues	262,865	170,102	687,539	477,878
Operating Income	18,474	10,843	46,500	31,862
Depreciation and amortization	4,266	3,057	11,050	8,071
Capital expenditures, cash and non-cash	5,299	3,552	21,180	19,136
Total assets	655,543		655,543		388,262
LTL [Member]
Schedule of financial data of reportable segments
Revenues	151,069	144,190	436,232	423,426
Operating Income	5,478	10,907	20,154	31,693
Depreciation and amortization	912	614	2,531	2,396
Capital expenditures, cash and non-cash	2,975	1,651	5,532	3,611
Total assets	831,717		831,717		576,976
TMS [Member]
Schedule of financial data of reportable segments
Revenues	87,240	50,921	225,695	99,331
Operating Income	6,708	4,634	16,273	10,923
Depreciation and amortization	866	291	2,333	643
Capital expenditures, cash and non-cash	261	130	1,278	182
Total assets	235,762		235,762		162,718
Corporate, Non-Segment [Member]
Schedule of financial data of reportable segments
Operating Income	(5,380)	(2,725)	(11,455)	(7,284)
Depreciation and amortization	275	67	874	120
Capital expenditures, cash and non-cash	540	697	2,566	1,450
Total assets	4,716		4,716		0
Eliminations [Member]
Schedule of financial data of reportable segments
Revenues	(3,088)	(2,057)	(9,168)	(6,191)
Total assets	$ (480,337)		$ (480,337)		$ (256,076)