UNAUDITED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Cash flows from operating activities:
Net income	$ 64,318	$ 40,609
Adjustments to reconcile net income to net cash flows provided by operating activities:
Depreciation and amortization of property and equipment	32,884	32,021
Amortization of intangible assets	1,734	3,009
Stock-based compensation expense	5,350	3,804
Deferred income taxes	1,364	712
Gain on sale of property and equipment	(2,473)	(1,967)
Other non-cash items	1,171	654
Changes in operating assets and liabilities, net of acquisitions:
Accounts receivable, net	23,929	(12,869)
Contract assets, net	(33,642)	(4,754)
Receivable for insurance claims in excess of deductibles	(5,273)	3,103
Other assets	(5,786)	7,074
Accounts payable	29,874	7,596
Contract liabilities	(8,515)	20,161
Accrued self insurance	5,571	(2,257)
Other liabilities	(2,291)	31,730
Net cash flows provided by operating activities	108,215	128,626
Cash flows from investing activities:
Proceeds from sale of property and equipment	2,489	2,147
Purchases of property and equipment	(32,701)	(27,470)
Net cash flows used in investing activities	(30,212)	(25,323)
Cash flows from financing activities:
Net repayments under revolving lines of credit	0	(65,189)
Payment of principal obligations under equipment notes	(24,409)	(30,441)
Payment of principal obligations under finance leases	(336)	(914)
Proceeds from exercise of stock options	483	306
Repurchase of common shares	(3,352)	(426)
Other financing activities	11	60
Net cash flows used in financing activities	(27,603)	(96,604)
Effect of exchange rate changes on cash	(62)	(150)
Net increase in cash and cash equivalents	50,338	6,549
Cash and cash equivalents:
Beginning of period	22,668	12,397
End of period	$ 73,006	$ 18,946