Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
OPERATING ACTIVITIES
Net income	$ 13,238	$ 17,318
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	26,761	22,451
Deferred income taxes	7,541	2,515
Stock-based compensation	936	284
Loss (gain) on disposal of property and equipment	229	(3,841)
Changes in certain working capital items:
Trade receivables	(6,096)	(4,324)
Prepaid expenses and other current assets	470	(396)
Accounts payable, accrued liabilities, and accrued expenses	(55)	(158)
Accrued income taxes	(2,967)	1,920
Net cash provided by operating activities	40,057	35,769
INVESTING ACTIVITIES
Proceeds from sale of property and equipment	2,409	13,753
Purchases of property and equipment, net of trades	(42,092)	(34,209)
Change in other assets	51	4
Net cash used in investing activities	(39,632)	(20,452)
FINANCING ACTIVITIES
Payments of cash dividends	(1,628)	(1,640)
Shares withheld for employee taxes related to stock-based compensation	(239)	(107)
Repurchases of common stock	(12,278)	0
Net cash used in financing activities	(14,145)	(1,747)
Net (decrease) increase in cash, cash equivalents and restricted cash	(13,720)	13,570
CASH, CASH EQUIVALENTS AND RESTRICTED CASH
Beginning of period	96,076	182,938
Ending Period	82,356	196,508
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION
Cash paid (received) during the period for income taxes, net of refunds	(109)	235
Noncash investing and financing activities:
Purchased property and equipment in accounts payable	8,554	7,309
Sold revenue equipment and property in other current assets	2,000	4,611
RECONCILIATION OF CASH, CASH EQUIVALENTS AND RESTRICTED CASH
Cash and Cash Equivalents, at Carrying Value	64,183	176,303
Restricted Cash and Investments, Current	1,533	2,638
Restricted Cash and Cash Equivalents, Noncurrent	16,640	17,567
Ending Period	$ 82,356	$ 196,508