Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
OPERATING ACTIVITIES
Net income	$ 14,775	$ 133,584	$ 79,277
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	199,039	133,047	104,232
Deferred income taxes	(18,081)	2,412	(5,869)
Stock-based compensation expense	1,620	1,399	1,150
Debt-related amortization	1,069	360	0
Gain on disposal of property and equipment	(41,087)	(96,906)	(37,438)
Changes in certain working capital items (net of acquisition):
Trade receivables	37,079	20,033	2,765
Prepaid expenses and other current assets	9,065	845	3,657
Accounts payable, accrued liabilities, and accrued expenses	(30,998)	(1,227)	(18,476)
Accrued income taxes	(7,214)	1,166	(5,880)
Net cash provided by operating activities	165,267	194,713	123,418
INVESTING ACTIVITIES
Proceeds from sale of property and equipment	137,319	172,750	130,184
Purchases of property and equipment, net of trades	(208,596)	(160,568)	(132,640)
Acquisition of business, net of cash acquired	0	(675,852)	0
Change in other assets	3,410	411	(191)
Net cash used in investing activities	(67,867)	(663,259)	(2,647)
FINANCING ACTIVITIES
Cash dividends paid	(6,322)	(6,318)	(45,872)
Proceeds from issuance of long-term debt	0	447,343	0
Shares withheld for employee taxes related to stock-based compensation	(290)	(290)	(247)
Repayments on finance leases and debt	(114,078)	(81,478)	0
Repurchases of common stock	0	0	(32,025)
Net cash provided by (used in) financing activities	(120,690)	359,257	(78,144)
Net increase (decrease) in cash and cash equivalents	(23,290)	(109,289)	42,627
CASH, CASH EQUIVALENTS AND RESTRICTED CASH
Beginning of period	64,478	173,767	131,140
End of period	41,188	64,478	173,767
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION
Cash paid during the period for interest expense	22,444	6,384	0
Cash paid during the period for income taxes, net of refunds	30,135	44,010	38,519
Noncash investing and financing activities:
Fair value of revenue equipment traded	0	428	0
Purchased property and equipment in accounts payable	3,912	11,938	9,019
Sold revenue equipment and property in other current assets	2,516	1,558	1,512
Right-of-use assets obtained in exchange for operating lease liabilities	8,236	3,345	0
RECONCILIATION OF CASH, CASH EQUIVALENTS AND RESTRICTED CASH
Cash and cash equivalents	28,123	49,462	157,742
Restricted cash included in other current assets	332	752	928
Restricted cash included in other assets	12,733	14,264	15,097
Total cash, cash equivalents and restricted cash	$ 41,188	$ 64,478	$ 173,767