Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities:
Net (loss) income	$ (42,718)	$ 8,477	$ 42,503
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for losses on accounts receivable	3,134	255	507
Deferral (reversal) of gain on sales to equity method investee, net	14	(7)	(189)
Depreciation and amortization	65,480	80,529	75,859
Impairment of property and equipment	26,569	0	0
Amortization of deferred financing fees	154	147	148
Deferred income tax (benefit) expense	(15,092)	3,454	13,840
Income tax benefit (expense) arising from restricted share vesting and stock options exercised	167	(105)	(44)
Stock-based compensation expense	2,270	819	5,177
Equity in income of affiliate	(3,944)	(7,017)	(7,732)
Return on investment in affiliated company	1,470	1,225	1,960
(Gain) loss on disposition of property and equipment	(7,677)	(2,829)	298
Loss on disposition of reportable segment	40,431	0	0
Return on investment in available-for-sale securities	(25)	13	(13)
Changes in operating assets and liabilities:
Receivables and advances	(60,849)	(6,706)	(27,199)
Prepaid expenses and other assets	531	487	(2,127)
Inventory and supplies	1,091	(143)	168
Insurance and claims accrual	32,203	945	2,412
Accounts payable and accrued expenses	19,831	(15,513)	19,232
Net cash flows provided by operating activities	63,040	64,031	124,800
Cash flows from investing activities:
Acquisition of Landair Holdings, Inc., net of cash acquired	0	0	(105,946)
Redemption (purchase) of available-for-sale securities	1,442	(1,365)	(1,496)
Acquisition of property and equipment	(94,049)	(138,273)	(75,142)
Proceeds from disposition of reportable segment	108,375	0	0
Proceeds from disposition of property and equipment	122,278	46,609	61,687
Net cash flows provided (used in) investing activities	138,046	(93,029)	(120,897)
Cash flows from financing activities:
Change in checks outstanding in excess of bank balances	839	(1,265)	1,857
Proceeds from issuance of notes payable	75,591	107,251	100,811
Repayments of notes payable	(289,834)	(44,278)	(89,569)
Repayments of capital lease obligations	(20,083)	(7,225)	(3,883)
Proceeds under revolving credit facility	1,341,678	1,734,338	1,598,213
Repayments under revolving credit facility	(1,326,678)	(1,738,249)	(1,603,309)
Payment of minimum tax withholdings on stock compensation	(297)	(1,110)	(242)
Debt refinancing costs	0	0	(10)
Common stock repurchased	(17,486)	0	0
Net cash flows (used in) provided by financing activities	(236,270)	49,462	3,868
Net change in cash and cash equivalents	(35,184)	20,464	7,771
Cash and cash equivalents at beginning of year	43,591	23,127	15,356
Cash and cash equivalents at end of year	8,407	43,591	23,127
Supplemental disclosure of cash flow information:
Interest, net of capitalized interest	7,365	11,026	8,568
Income taxes	870	752	(5,388)
Non-cash transactions during the year for:
Equipment purchased under finance leases	3,258	0	19,638
Contingent liabilities	$ 44,151	$ 0	$ 0