Consolidated Statements of Operations (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Income Statement [Abstract]
Revenues	$ 1,073,354	$ 843,627	$ 632,018
Operating expenses:
Purchased transportation costs	753,459	620,343	494,045
Personnel and related benefits	119,955	87,178	61,853
Other operating expenses	120,718	83,625	41,168
Depreciation and amortization	9,499	4,978	3,114
Acquisition transaction expenses	773	1,368	569
Restructuring and IPO related expenses	0	0	1,500
Total operating expenses	1,004,404	797,492	602,249
Operating income	68,950	46,135	29,769
Interest expense:
Interest on long-term debt	7,981	4,135	7,954
Dividends on preferred stock subject to mandatory redemption	49	200	200
Total interest expense	8,030	4,335	8,154
Loss on early extinguishment of debt	0	0	15,916
Income before provision for income taxes	60,920	41,800	5,699
Provision for income taxes	23,390	15,929	2,108
Net income	37,530	25,871	3,591
Accretion of Series B preferred stock	0	0	765
Net income available to common stockholders	$ 37,530	$ 25,871	$ 2,826
Earnings per share available to common stockholders:
Basic (in usd per share)	$ 1.21	$ 0.85	$ 0.11
Diluted (in usd per share)	$ 1.16	$ 0.82	$ 0.11
Weighted average common stock outstanding:
Basic (shares)	31,040	30,432	25,779
Diluted (shares)	32,425	31,545	26,777