CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Income Statement [Abstract]
Revenue	$ 324,315	$ 306,392	$ 627,095	$ 602,687
Direct costs	206,565	190,896	395,391	374,503
Operating costs and expenses:
Indirect and selling expenses	90,410	86,240	180,069	175,042
Depreciation and amortization	4,045	4,299	8,514	8,818
Amortization of intangible assets	2,270	2,749	4,514	5,483
Total operating costs and expenses	96,725	93,288	193,097	189,343
Operating income	21,025	22,208	38,607	38,841
Interest expense	(2,167)	(2,537)	(3,833)	(4,488)
Other (expense) income	(318)	226	(214)	335
Income before income taxes	18,540	19,897	34,560	34,688
Provision for income taxes	4,923	7,960	8,526	12,574
Net income	$ 13,617	$ 11,937	$ 26,034	$ 22,114
Earnings per Share:
Basic	$ 0.72	$ 0.64	$ 1.39	$ 1.17
Diluted	$ 0.71	$ 0.63	$ 1.36	$ 1.15
Weighted-average Shares:
Basic	18,806	18,775	18,738	18,840
Diluted	19,209	19,086	19,208	19,252
Cash dividends declared per common share	$ 0.14		$ 0.28
Other comprehensive (loss) income, net of tax	$ (3,317)	$ 2,100	$ (1,708)	$ 2,472
Comprehensive income, net of tax	$ 10,300	$ 14,037	$ 24,326	$ 24,586