Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Operating activities
Net income (loss)	$ 16,120	$ 9,969
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Deferred income tax provision	3,764	1,543
Depreciation and amortization	62,049	68,104
Losses on sale of equipment	3,047	9,767
Share based compensation	5,294	3,421
Other	546	3,186
Unrealized gain on equity investment	(8,129)
Changes in operating assets and liabilities, net of acquisitions:
Receivables	(38,064)	(8,354)
Prepaid insurance and licenses	(7,486)	(11,747)
Operating supplies	(3,420)	(204)
Other assets	(8,284)	(3,047)
Accounts payable and other accrued liabilities	36,762	21,413
Accrued wages and benefits	8,105	7,863
Net cash provided by operating activities	70,304	101,914
Investing activities
Payments for purchases of property and equipment	(141,068)	(129,582)
Proceeds from sales of property and equipment	70,016	36,192
Other		(1,880)
Net cash used in investing activities	(71,052)	(95,270)
Financing activities
Borrowings under lines of credit	235,612	231,254
Payments under lines of credit	(210,612)	(231,254)
Borrowings under long-term debt	83,959	228,981
Payments of long-term debt and finance leases	(110,759)	(231,340)
Payments of financing costs	(100)	(1,391)
Payments of long-term consideration for business acquisition		(1,000)
Tax withholding related to net share settlement of restricted stock awards	(1,211)	(135)
Proceeds from issuance of common stock under ESPP	1,285	851
Proceeds from long-term consideration for sale of subsidiary	460	438
Book overdraft	2,604	(1,313)
Net cash used in financing activities	1,238	(4,909)
Net change in cash and cash equivalents	490	1,735
Cash and cash equivalents:
Beginning of period	5,505	5,687
End of period	5,995	7,422
Supplemental disclosure of cash flow information
Cash paid during the year for interest	10,281	13,479
Cash paid during the year for income taxes	1,213	497
Supplemental disclosure of significant noncash investing and financing activities
Subsidiary stock issued in business combination		7,278
Finance lease additions	5,572
Property and equipment amounts accrued in accounts payable	$ 3,887	$ 1,252