CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net income	$ 21,154	$ 21,431	$ 27,302
Adjustments to reconcile net income to net cash flows provided by (used in) operating activities -
Depreciation and amortization of property and equipment	38,077	38,236	37,458
Amortization of intangible assets	499	886	571
Stock-based compensation expense	4,376	4,674	4,837
Deferred income taxes	(5,091)	4,205	1,558
Gain on sale of property and equipment	(3,664)	(1,341)	(2,257)
Other non-cash items	1,194	194	200
Changes in operating assets and liabilities, net of acquisitions
Accounts receivable, net	(46,190)	(27,485)	(17,765)
Costs and estimated earnings in excess of billings on uncompleted contracts	(7,611)	(17,001)	(4,597)
Receivable for insurance claims in excess of deductibles	(39)	(7,187)	1,021
Other assets	(2,213)	3,730	(5,634)
Accounts payable	8,149	17,322	6,742
Billings in excess of costs and estimated earnings on uncompleted contracts	(13,502)	(707)	1,003
Accrued self-insurance	2,765	5,617	(2,616)
Other liabilities	(7,102)	11,916	(4,823)
Net cash flows provided by (used in) operating activities	(9,198)	54,490	43,000
Cash flows from investing activities:
Proceeds from sale of property and equipment	4,342	3,299	2,758
Cash paid for acquisitions, net of cash acquired	0	(12,056)	(13,087)
Purchases of property and equipment	(30,843)	(25,371)	(46,599)
Net cash flows used in investing activities	(26,501)	(34,128)	(56,928)
Cash flows from financing activities:
Net borrowings under revolving lines of credit	19,890	59,070	0
Payment of principal obligations under capital leases	(1,203)	(740)	0
Proceeds from exercise of stock options	1,232	6,218	1,923
Repurchase of common shares	(3,058)	(101,483)	(27,582)
Other financing activities	28	1,396	1,748
Net cash flows provided by (used in) financing activities	16,889	(35,539)	(23,911)
Effect of exchange rate changes on cash	307	(774)	0
Net decrease in cash and cash equivalents	(18,503)	(15,951)	(37,839)
Cash and cash equivalents:
Beginning of period	23,846	39,797	77,636
End of period	5,343	23,846	39,797
Supplemental Cash Flow Information:
Income taxes payments	6,597	6,274	16,960
Interest payments	2,259	1,114	591
Noncash investing activities:
Acquisition of property and equipment for which payment is pending	2,050	614	1,328
Acquisition of property under capital lease arrangements	0	5,658	0
Noncash financing activities:
Capital lease obligations initiated	0	5,658	0
Share repurchases that have not settled	$ 0	$ 0	$ 896