Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Operating activities
Net income (loss)	$ 2,661	$ (9,232)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Deferred income tax provision (benefit)	1,241	(1,882)
Depreciation and amortization	20,777	22,597
Losses on sale of equipment	1,605	3,206
Share based compensation	2,134	836
Other	184	2,652
Changes in operating assets and liabilities:
Receivables	(23,448)	(3,183)
Prepaid insurance and licenses	(3,471)	(5,784)
Operating supplies	(1,178)	(151)
Other assets	(1,337)	386
Accounts payable and other accrued liabilities	14,459	8,788
Accrued wages and benefits	1,694	1,845
Net cash provided by operating activities	15,321	20,078
Investing activities
Payments for purchases of property and equipment	(21,974)	(76,761)
Proceeds from sales of property and equipment	19,955	9,650
Other		(2,000)
Net cash used in investing activities	(2,019)	(69,111)
Financing activities
Borrowings under lines of credit	47,600	147,654
Payments under lines of credit	(34,400)	(70,654)
Borrowings under long-term debt	12,288	142,644
Payments of long-term debt and finance leases	(42,185)	(171,266)
Payments of financing costs	(100)	(1,255)
Payments of long-term consideration for business acquisition		(1,000)
Tax withholding related to net share settlement of restricted stock awards	(915)	(91)
Proceeds from issuance of common stock under ESPP	538	420
Proceeds from long-term consideration for sale of subsidiary	151	144
Book overdraft	2,584	2,376
Net cash (used in) provided by financing activities	(14,439)	48,972
Net change in cash and cash equivalents	(1,137)	(61)
Cash and cash equivalents:
Beginning of period	5,505	5,687
End of period	4,368	5,626
Supplemental disclosure of cash flow information
Cash paid during the year for interest	3,497	4,215
Cash paid during the year for income taxes	(166)	243
Supplemental disclosure of significant noncash investing and financing activities
Property and equipment amounts accrued in accounts payable	$ 1,204	$ 2,397