Restatement of Previously Issued Financial Statements (Impact on Consolidated Statements of Operations) (Details) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended		56 Months Ended
		Mar. 31, 2016 USD ($) $ / shares shares	Mar. 31, 2015 USD ($) $ / shares shares	Sep. 30, 2015 company
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenues	[1]	$ 466,546	$ 488,834
Operating expenses:
Purchased transportation costs	[1]	308,039	327,377
Personnel and related benefits	[1]	68,349	62,964
Other operating expenses	[1]	73,873	71,212
Depreciation and amortization	[1]	9,209	6,807
Total operating expenses	[1]	459,470	468,360
Operating income	[1]	7,076	20,474
Interest expense	[1]	5,608	4,609
Income before provision for income taxes	[1]	1,468	15,865
Provision for income taxes	[1]	568	6,045
Net income	[1],[2]	$ 900	$ 9,820
Earnings per share:
Basic (in dollars per share) | $ / shares	[1]	$ 0.02	$ 0.26
Diluted (in dollars per share) | $ / shares	[1]	$ 0.02	$ 0.25
Weighted average common stock outstanding:
Basic (in shares) | shares	[1]	38,284	38,011
Diluted (in shares) | shares	[1]	38,372	39,324
As Previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenues		$ 465,632	$ 488,970
Operating expenses:
Purchased transportation costs		308,474	328,491
Personnel and related benefits		67,601	62,055
Other operating expenses		69,415	64,745
Depreciation and amortization		9,536	6,877
Total operating expenses		455,026	462,168
Operating income		10,606	26,802
Interest expense		5,608	4,609
Income before provision for income taxes		4,998	22,193
Provision for income taxes		1,933	8,589
Net income		$ 3,065	$ 13,604
Earnings per share:
Basic (in dollars per share) | $ / shares		$ 0.08	$ 0.36
Diluted (in dollars per share) | $ / shares		$ 0.08	$ 0.35
Weighted average common stock outstanding:
Basic (in shares) | shares		38,284	38,011
Diluted (in shares) | shares		38,372	39,341
Adjustments
Operating expenses:
Net income		$ (2,165)	$ (3,784)
Adjustments | Receivables & Related Reserves
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenues		1,914	(136)
Operating expenses:
Purchased transportation costs		0	0
Personnel and related benefits		0	0
Other operating expenses		553	1,979
Depreciation and amortization		0	0
Total operating expenses		553	1,979
Operating income		1,361	(2,115)
Interest expense		0	0
Income before provision for income taxes		1,361	(2,115)
Provision for income taxes		0	0
Net income		1,361	(2,115)
Adjustments | Unrecorded Charges & Contingent Liabilities
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenues		(1,000)	0
Operating expenses:
Purchased transportation costs		(435)	(1,114)
Personnel and related benefits		748	909
Other operating expenses		34	2,032
Depreciation and amortization		0	0
Total operating expenses		347	1,827
Operating income		(1,347)	(1,827)
Interest expense		0	0
Income before provision for income taxes		(1,347)	(1,827)
Provision for income taxes		0	0
Net income		(1,347)	(1,827)
Adjustments | Insurance Reserves & Related Receivables
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenues		0	0
Operating expenses:
Purchased transportation costs		0	0
Personnel and related benefits		0	0
Other operating expenses		1,279	1,373
Depreciation and amortization		0	0
Total operating expenses		1,279	1,373
Operating income		(1,279)	(1,373)
Interest expense		0	0
Income before provision for income taxes		(1,279)	(1,373)
Provision for income taxes		0	0
Net income		(1,279)	(1,373)
Adjustments | Capital Improvements & Aircraft Spare Parts
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenues		0	0
Operating expenses:
Purchased transportation costs		0	0
Personnel and related benefits		0	0
Other operating expenses		2,592	1,083
Depreciation and amortization		(327)	(70)
Total operating expenses		2,265	1,013
Operating income		(2,265)	(1,013)
Interest expense		0	0
Income before provision for income taxes		(2,265)	(1,013)
Provision for income taxes		0	0
Net income		(2,265)	(1,013)
Adjustments | Income Taxes & Debt Reclassification
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenues		0	0
Operating expenses:
Purchased transportation costs		0	0
Personnel and related benefits		0	0
Other operating expenses		0	0
Depreciation and amortization		0	0
Total operating expenses		0	0
Operating income		0	0
Interest expense		0	0
Income before provision for income taxes		0	0
Provision for income taxes		(1,365)	(2,544)
Net income		$ 1,365	$ 2,544
Non-Public Companies
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Number of businesses acquired | company				25

[1] See Note 13 “Restatement of Previously Issued Financial Statements

[2] See Note 13 “Restatement of Previously Issued Financial Statements.”