CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Statement [Abstract]
Revenue	$ 332,968	$ 305,301	$ 960,063	$ 907,988
Direct costs	213,060	189,992	608,451	564,495
Operating costs and expenses:
Indirect and selling expenses	88,960	84,558	269,029	259,600
Depreciation and amortization	4,210	4,613	12,724	13,431
Amortization of intangible assets	2,516	2,742	7,030	8,225
Total operating costs and expenses	95,686	91,913	288,783	281,256
Operating income	24,222	23,396	62,829	62,237
Interest expense	(2,240)	(2,175)	(6,073)	(6,663)
Other (expense) income	(351)	(311)	(565)	24
Income before income taxes	21,631	20,910	56,191	55,598
Provision for income taxes	4,960	7,218	13,486	19,792
Net income	$ 16,671	$ 13,692	$ 42,705	$ 35,806
Earnings per Share:
Basic	$ 0.88	$ 0.73	$ 2.27	$ 1.90
Diluted	$ 0.86	$ 0.72	$ 2.22	$ 1.86
Weighted-average Shares:
Basic	18,873	18,666	18,783	18,807
Diluted	19,306	19,024	19,256	19,218
Cash dividends declared per common share	$ 0.14		$ 0.42
Other comprehensive (loss) income, net of tax	$ (568)	$ 558	$ (2,276)	$ 3,030
Comprehensive income, net of tax	$ 16,103	$ 14,250	$ 40,429	$ 38,836