Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Cash flows from operating activities:
Net income	$ 10,853	$ 28,855
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for losses on accounts receivable	(531)	196
(Reversal)/deferral of gain on sales to equity method investee	(169)	38
Depreciation and amortization	52,142	43,741
Amortization of deferred financing fees	224	199
Deferred income tax (benefit) expense	(5,505)	1,798
Casualty premium credit		(3,600)
Income tax benefit arising from restricted share vesting	560	(1,757)
Unrealized gain on ineffective portion of fuel hedges		(1,290)
Return of cash collateral on fuel hedge		5,000
Stock-based compensation expense	1,114	1,136
Equity in income of affiliate	(2,450)	(3,720)
Return on investment in affiliated company	1,470
Loss (gain) on disposition of property and equipment	90	(373)
Changes in operating assets and liabilities:
Receivables and advances	43,743	22,655
Prepaid expenses and other assets	(1,028)	1,102
Inventory and supplies	(108)	250
Insurance and claims accrual	(4,276)	(3,599)
Accounts payable and accrued expenses	(14,040)	(12,071)
Net cash flows provided by operating activities	82,089	78,560
Cash flows from investing activities:
Acquisition of property and equipment	(100,920)	(145,611)
Proceeds from disposition of property and equipment	54,959	31,104
Net cash flows used in investing activities	(45,961)	(114,507)
Cash flows from financing activities:
Change in checks outstanding in excess of bank balances	(3,399)
Proceeds from issuance of notes payable	62,969	93,419
Proceeds from the exercise of stock options	32	1,092
Income tax benefit arising from restricted share vesting		1,757
Repayments of notes payable	(103,627)	(59,337)
Repayments of capital lease obligations	(3,711)	(1,286)
Proceeds under revolving credit facility	762,338	635,784
Repayments under revolving credit facility	(749,504)	(635,784)
Payment of minimum tax withholdings on stock compensation	(581)	(1,786)
Common stock repurchased		(4,994)
Debt refinancing costs	(108)	(226)
Net cash (used in) provided by financing activities	(35,591)	28,639
Net change in cash and cash equivalents	537	(7,308)
Cash and cash equivalents at beginning of period	4,490	21,330
Cash and cash equivalents at end of period	$ 5,027	$ 14,022