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 including noncontrolling interests	$ 55,272	$ 64,896	$ 57,440
Adjustments to reconcile net income to net cash provided by operating activities—
Amortization of identifiable intangible assets	17,404	8,185	7,481
Depreciation expense	20,052	17,981	15,935
Goodwill impairment	1,105
Bad debt expense (benefit)	182	(27)	1,552
Deferred tax provision (benefit)	4,178	(1,239)	(414)
Amortization of debt financing costs	376	367	317
Gain on sale of assets	(670)	(761)	(880)
Changes in the fair value of contingent earn-out obligations	(3,715)	(731)	(225)
Stock-based compensation	6,377	5,041	5,609
(Increase) decrease in-
Receivables, net	(37,799)	7,038	(3,584)
Inventories	(584)	213	956
Prepaid expenses and other current assets	2,467	(8,850)	364
Costs and estimated earnings in excess of billings	1,869	3,144	(3,630)
Other noncurrent assets	1,005	(143)	(479)
Increase (decrease) in-
Accounts payable and accrued liabilities	22,068	2,736	11,617
Billings in excess of costs and estimated earnings	13,265	(8,351)	7,908
Other long-term liabilities	11,238	1,689	(2,100)
Net cash provided by operating activities	114,090	91,188	97,867
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of property and equipment	(35,467)	(23,217)	(20,808)
Proceeds from sales of property and equipment	1,359	1,062	1,338
Cash paid for acquisitions, net of cash acquired	(94,860)	(57,163)	(6,158)
Net cash used in investing activities	(128,968)	(79,318)	(25,628)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from revolving line of credit	177,000	144,000	24,500
Payments on revolving line of credit	(132,000)	(154,000)	(53,000)
Payments on other debt	(835)	(592)
Payments on capital lease obligations	(256)	(251)	(443)
Debt financing costs		(789)
Payments of dividends to stockholders	(10,987)	(10,264)	(9,358)
Share repurchase	(9,007)	(13,088)	(8,330)
Shares received in lieu of tax withholding	(1,419)	(1,304)	(937)
Excess tax benefit of stock-based compensation			1,240
Proceeds from exercise of options	2,052	1,578	3,738
Distributions to noncontrolling interests			(4,904)
Deferred acquisition payments	(2,802)	(1,350)
Payments for contingent consideration arrangements	(2,400)	(200)	(345)
Net cash provided by (used in) financing activities	19,346	(36,260)	(47,839)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	4,468	(24,390)	24,400
CASH AND CASH EQUIVALENTS, beginning of year	32,074	56,464	32,064
CASH AND CASH EQUIVALENTS, end of year	$ 36,542	$ 32,074	$ 56,464