Consolidated Statements of Cash Flows $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
OPERATING ACTIVITIES
Net income	$ 70,806	$ 72,967	$ 72,677
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	110,381	100,932	101,329
Deferred income taxes	8,148	4,699	2,755
Stock-based Compensation	2,092	2,065	539
Gain on disposal of property and equipment	(14,830)	(31,341)	(24,963)
Changes in certain working capital items:
Trade receivables	1,176	6,676	15,338
Prepaid expenses and other current assets	(3,628)	509	1,227
Accounts payable, accrued liabilities, and accrued expenses	3,062	(10,758)	(26,012)
Accrued income taxes	1,643	623	3,653
Net cash provided by operating activities	178,850	146,372	146,543
INVESTING ACTIVITIES
Proceeds from sale of property and equipment	93,160	92,942	130,752
Purchases of property and equipment, net of trades	(204,337)	(163,780)	(169,276)
Acquisition of business, net of cash acquired	0	(61,927)	0
Change in other assets	129	(26)	710
Net cash (used in) provided by investing activities	(111,048)	(132,791)	(37,814)
FINANCING ACTIVITIES
Cash dividends paid	(6,502)	(6,563)	(6,589)
Shares withheld for employee taxes related to stock-based compensation	(582)	(532)	(213)
Repayments on acquired debt	0	(93,348)	0
Repurchases of common stock	(25,654)	0	(25,087)
Net cash used in financing activities	(32,738)	(100,443)	(31,889)
Net increase (decrease) in cash, cash equivalents and restricted cash	35,064	(86,862)	76,840
CASH, CASH EQUIVALENTS AND RESTRICTED CASH
Beginning of period	96,076	182,938	106,098
End of Period	131,140	96,076	182,938
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION
Interest Paid	0	929	0
Cash paid during the period for income taxes, net of refunds	13,664	18,888	12,832
Noncash investing and financing activities:
Purchased property and equipment in accounts payable	2,172	1,476	1,944
Sold revenue equipment in other current assets	3,383	1,282	3,783
Treasury stock acquired in accounts payable	485	0	0
RECONCILIATION OF CASH, CASH EQUIVALENTS AND RESTRICTED CASH
Cash and Cash Equivalents	113,852	76,684	161,448
Restricted Cash included in other current assets	1,075	1,594	3,105
Restricted Cash included in other assets	16,213	17,798	18,385
End of Period	$ 131,140	$ 96,076	$ 182,938