Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Cash flows from operating activities:
Net income	$ 7,984	$ 21,228
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for losses on accounts receivable	(457)	91
(Reversal)/deferral of gain on sales to equity method investee	(123)	75
Depreciation and amortization	33,235	28,973
Amortization of deferred financing fees	156	139
Deferred income tax (benefit) expense	(6,796)	1,815
Casualty premium credit		(3,600)
Income tax benefit arising from restricted share vesting	560	(1,757)
Unrealized gain on ineffective portion of fuel hedges		(969)
Return of cash collateral on fuel hedge		5,000
Stock-based compensation expense	804	800
Equity in income of affiliate	(2,000)	(2,720)
Return on investment in affiliated company	1,470
Loss on disposition of property and equipment	(331)	(297)
Changes in operating assets and liabilities:
Receivables and advances	49,320	16,557
Prepaid expenses and other assets	(3,586)	(1,841)
Inventory and supplies	(206)	86
Insurance and claims accrual	(4,080)	(483)
Accounts payable and accrued expenses	(11,569)	(6,188)
Net cash flows provided by operating activities	64,381	56,909
Cash flows from investing activities:
Acquisition of property and equipment	(60,673)	(37,131)
Proceeds from disposition of property and equipment	49,432	21,620
Net cash flows used in investing activities	(11,241)	(15,511)
Cash flows from financing activities:
Change in checks outstanding in excess of bank balances	(4,698)
Proceeds from issuance of notes payable	40,403	5,098
Proceeds from the exercise of stock options	32	1,092
Income tax benefit arising from restricted share vesting		1,757
Repayments of notes payable	(91,229)	(44,262)
Repayments of capital lease obligations	(877)	(857)
Proceeds under revolving credit facility	524,397	475,190
Repayments under revolving credit facility	(516,536)	(475,190)
Payment of minimum tax withholdings on stock compensation	(581)	(1,786)
Debt refinancing costs	(108)
Net cash used in financing activities	(49,197)	(38,958)
Net change in cash and cash equivalents	3,943	2,440
Cash and cash equivalents at beginning of period	4,490	21,330
Cash and cash equivalents at end of period	$ 8,433	$ 23,770