Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 30, 2021
Cash flows from operating activities:
Net income (loss)	$ 55,229	$ 108,682	$ 60,731	$ 60,731
Adjustments to reconcile net income to net cash provided by operating activities:
(Reversal of) provision for losses on accounts receivable	(258)	367	1,338
(Reversal) deferral of gain on sales to equity method investee, net	(16)	(39)	52
Depreciation and amortization	69,943	57,512	53,881
Deferred income tax benefit	18,701	13,968	18,413
Income tax expense arising from restricted share vesting and stock options exercised	(2,226)	(526)	(334)
Stock-based compensation expense	7,100	6,587	9,059
Income from equity method investment	(21,384)	(25,193)	(14,782)
Return on investment in affiliated company	9,800	14,700	4,900
Gain on disposition of property and equipment	(12,585)	(40,322)	(3,799)
Return on investment in available-for-sale securities	0	0	(63)
Changes in operating assets and liabilities:
Receivables and advances	(22,416)	39,465	(36,544)
Prepaid expenses and other assets	(3,997)	(3,832)	(710)
Inventory and supplies	(317)	(193)	(204)
Insurance and claims accrual	(3,542)	(5,729)	(31,653)
Accounts payable and accrued expenses	(9,191)	(6,217)	12,933
Net cash flows provided by operating activities	84,841	159,230	73,218
Cash flows from investing activities:
Acquisitions, net of cash acquired	(107,934)	(38,501)	0
Other investments	(2,204)	(241)	(13)
Redemption of available-for-sale securities	0	0	1,508
Acquisition of property and equipment	(217,607)	(100,468)	(35,285)
Proceeds from disposition of property and equipment	91,824	53,002	44,134
Net cash flows (used) provided by investing activities	(235,921)	(86,208)	10,344
Cash flows from financing activities:
Change in checks outstanding in excess of bank balances	0	(216)	(1,215)
Cash dividend	(5,781)	(4,287)	0
Proceeds from issuance of notes payable	154,093	95,151	0
Proceeds from exercise of stock options	236	384	0
Repayments of notes payable	(30,390)	(11,956)	(14,397)
Repayments of finance lease obligations	(5,619)	(5,516)	(5,626)
Proceeds under revolving credit facility	139,837	60,226	644,874
Repayments under revolving credit facility	(128,258)	(60,226)	(695,513)
Payment of minimum tax withholdings on stock compensation	(4,792)	(1,606)	(1,332)
Payment of contingent liability	(9,187)	0	0
Common stock repurchased	(25,430)	(84,723)	(10,348)
Net cash flows provided by (used in) financing activities	84,709	(12,769)	(83,557)
Net change in cash and cash equivalents	(66,371)	60,253	5
Cash and cash equivalents at beginning of year	68,665	8,412	8,407	$ 8,407
Cash and cash equivalents at end of year	2,294	68,665	8,412
Supplemental disclosure of cash flow information:
Interest, net of capitalized interest	5,319	3,306	2,762
Income taxes	4,186	16,653	10,236
Non-cash transactions during the year for:
Equipment acquired under finance leases	5,938	458	0
Equipment acquired under operating leases	3,992	48,515	15,795
Contingent consideration associated with acquisitions	11,802	16,210	0
Other contingent liabilities	$ (800)	$ (1,000)	$ (3,412)