Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenues:
Total revenues	$ 84,890	$ 80,369	$ 258,992	$ 247,296
Operating expenses:
Selling and marketing	31,051	29,225	96,771	90,355
General and administrative	11,192	10,083	32,871	30,672
Depreciation	1,965	1,607	6,056	4,775
Amortization of intangible assets	402	197	770	582
Acquisition and integration costs	977		1,306
Total operating expenses	79,948	73,620	245,311	227,198
Income from operations	4,942	6,749	13,681	20,098
Other income, net	319	146	472	248
Losses on investments, net	(17)	(772)	(62)	(997)
Income before income taxes	5,244	6,123	14,091	19,349
Income tax expense	1,294	2,170	4,086	6,302
Net income	$ 3,950	$ 3,953	$ 10,005	$ 13,047
Basic income per common share	$ 0.22	$ 0.22	$ 0.55	$ 0.73
Diluted income per common share	$ 0.21	$ 0.22	$ 0.55	$ 0.72
Basic weighted average common shares outstanding	18,088	17,747	18,030	17,897
Diluted weighted average common shares outstanding	18,433	18,051	18,353	18,212
Cash dividends declared per common share	$ 0.20	$ 0.19	$ 0.60	$ 0.57
Research Services [Member]
Revenues:
Total revenues	$ 56,332	$ 54,235	$ 166,332	$ 160,553
Advisory Services and Events [Member]
Revenues:
Total revenues	28,558	26,134	92,660	86,743
Cost of Services and Fulfillment [Member]
Operating expenses:
Cost of services and fulfillment	$ 34,361	$ 32,508	$ 107,537	$ 100,814