Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues:
Total revenues	$ 357,575	$ 337,673	$ 326,095
Operating expenses:
Selling and marketing	131,824	123,917	116,898
General and administrative	43,920	41,906	40,579
Depreciation	7,955	6,648	7,812
Amortization of intangible assets	1,162	781	831
Acquisition and integration costs	3,787
Reorganization costs			1,026
Total operating expenses	335,150	310,124	295,321
Income from operations	22,425	27,549	30,774
Other income, net	674	301	740
Gains (losses) on investments, net	426	(479)	(805)
Income before income taxes	23,525	27,371	30,709
Income tax provision	8,145	12,231	13,058
Net income	$ 15,380	$ 15,140	$ 17,651
Basic income per common share	$ 0.85	$ 0.84	$ 0.98
Diluted income per common share	$ 0.84	$ 0.83	$ 0.97
Basic weighted average common shares outstanding	18,091	17,919	17,984
Diluted weighted average common shares outstanding	18,380	18,240	18,269
Research Services [Member]
Revenues:
Total revenues	$ 228,399	$ 216,471	$ 215,216
Advisory Services and Events [Member]
Revenues:
Total revenues	129,176	121,202	110,879
Cost of Services and Fulfillment [Member]
Operating expenses:
Cost of services and fulfillment	$ 146,502	$ 136,872	$ 128,175