Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
OPERATING ACTIVITIES
Net Income	$ 79,277	$ 70,806	$ 72,967
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	104,232	110,381	100,932
Deferred income taxes	(5,869)	8,148	4,699
Stock-based compensation expense	1,150	2,092	2,065
Gain on disposal of property and equipment	(37,438)	(14,830)	(31,341)
Changes in certain working capital items (net of acquisition):
Trade receivables	2,765	1,176	6,676
Prepaid expenses and other current assets	3,657	(3,628)	509
Accounts payable, accrued liabilities, and accrued expenses	(18,476)	3,062	(10,758)
Accrued income taxes	(5,880)	1,643	623
Net cash provided by operating activities	123,418	178,850	146,372
INVESTING ACTIVITIES
Proceeds from sale of property and equipment	130,184	93,160	92,942
Purchases of property and equipment, net of trades	(132,640)	(204,337)	(163,780)
Acquisition of business, net of cash acquired	0	0	(61,927)
Change in other assets	(191)	129	(26)
Net cash used in investing activities	(2,647)	(111,048)	(132,791)
FINANCING ACTIVITIES
Cash dividends paid	(45,872)	(6,502)	(6,563)
Shares withheld for employee taxes related to stock-based compensation	(247)	(582)	(532)
Repayments on acquired debt	0	0	(93,348)
Repurchases of common stock	(32,025)	(25,654)	0
Net cash used in financing activities	(78,144)	(32,738)	(100,443)
Net increase (decrease) in cash, cash equivalents and restricted cash	42,627	35,064	(86,862)
CASH, CASH EQUIVALENTS AND RESTRICTED CASH
Beginning of period	131,140	96,076	182,938
Period End	173,767	131,140	96,076
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION
Interest Paid	0	0	929
Cash paid during the period for income taxes, net of refunds	38,519	13,664	18,888
Noncash investing and financing activities:
Purchased property and equipment in accounts payable	9,019	2,172	1,476
Sold revenue equipment in other current assets	1,512	3,383	1,282
Treasury stock acquired in accounts payable	0	485	0
RECONCILIATION OF CASH, CASH EQUIVALENTS AND RESTRICTED CASH
Cash and cash equivalents	157,742	113,852	76,684
Restricted cash included in other current assets	928	1,075	1,594
Restricted cash included in other assets	15,097	16,213	17,798
Total cash, cash equivalents and restricted cash	$ 173,767	$ 131,140	$ 96,076