Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
OPERATING ACTIVITIES
Net Income	$ 13,734	$ 13,238
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	26,983	26,761
Deferred income taxes	(3,390)	7,541
Stock-based compensation	581	936
(Gain)/Loss on disposal of property and equipment	(4,232)	229
Changes in certain working capital items:
Trade receivables	(4,991)	(6,096)
Prepaid expenses and other current assets	4,053	470
Accounts payable, accrued liabilities, and accrued expenses	(2,554)	(55)
Accrued income taxes	5,248	(2,967)
Net cash provided by operating activities	35,432	40,057
INVESTING ACTIVITIES
Proceeds from sale of property and equipment	25,152	2,409
Purchases of property and equipment	(9,750)	(42,092)
Change in other assets	78	51
Net cash provided by (used in) investing activities	15,480	(39,632)
FINANCING ACTIVITIES
Payments of cash dividends	(1,599)	(1,628)
Shares withheld for employee taxes related to stock-based compensation	(96)	(239)
Repurchases of common stock	(15,022)	(12,278)
Net cash used in financing activities	(16,717)	(14,145)
Net increase (decrease) in cash, cash equivalents and restricted cash	34,195	(13,720)
CASH, CASH EQUIVALENTS AND RESTRICTED CASH
Beginning of period	131,140	96,076
Ending Period	165,335	82,356
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION
Cash paid (received) during the period for income taxes, net of refunds	2,825	(109)
Noncash investing and financing activities:
Purchased property and equipment in accounts payable	6,726	8,554
Sold revenue equipment and property in other current assets	212	2,000
RECONCILIATION OF CASH, CASH EQUIVALENTS AND RESTRICTED CASH
Cash and Cash Equivalents, at Carrying Value	148,212	64,183
Restricted Cash and Investments, Current	1,033	1,533
Restricted Cash and Cash Equivalents, Noncurrent	16,090	16,640
Ending Period	$ 165,335	$ 82,356