Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Cash flows from operating activities:
Net income	$ 3,797	$ 10,227
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for losses on accounts receivable	(123)	90
(Reversal)/Deferral of gain on sales to equity method investee	(43)	66
Depreciation and amortization	16,634	14,506
Gain (loss) on disposition of property and equipment	251	(124)
Amortization of deferred financing fees	77	65
Deferred income tax (benefit) expense	$ (6,726)	1,662
Unrealized gain on ineffective portion of fuel hedges		(340)
Return of cash collateral on fuel hedge		2,100
Stock-based compensation expense	$ 304	285
Equity in income of affiliate	(850)	(1,385)
Changes in operating assets and liabilities:
Receivables and advances	47,697	14,091
Prepaid expenses and other assets	2,027	1,801
Inventory and supplies	(185)	84
Insurance and claims accrual	(538)	1,237
Accounts payable and accrued expenses	(10,809)	(7,961)
Net cash flows provided by operating activities	51,513	36,404
Cash flows from investing activities:
Acquisition of property and equipment	(17,394)	(18,264)
Proceeds from disposition of property and equipment	28,593	11,042
Net cash flows provided by (used in) investing activities	11,199	$ (7,222)
Cash flows from financing activities:
Change in checks outstanding in excess of bank balances	(922)
Proceeds from issuance of notes payable	5,971	$ 5,098
Proceeds from the exercise of stock options	32	765
Repayments of notes payable	(74,235)	(37,892)
Repayments of capital lease obligations	(437)	(431)
Proceeds under revolving credit facility	287,444	249,077
Repayments under revolving credit facility	(280,733)	(249,077)
Payment of minimum tax withholdings on stock compensation	(575)	$ (1,762)
Debt refinancing costs	(57)
Net cash used in financing activities	(63,512)	$ (34,222)
Net change in cash and cash equivalents	(800)	(5,040)
Cash and cash equivalents at beginning of period	4,490	21,330
Cash and cash equivalents at end of period	$ 3,690	$ 16,290