Condensed Consolidated Statements of Operations (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Revenues:
Research	$ 274,620	$ 243,435
Consulting	74,563	70,630
Events	19,988	15,502
Total revenues	369,171	329,567
Costs and expenses:
Cost of services and product development	146,463	133,316
Selling, general and administrative	162,518	141,672
Depreciation	5,895	6,271
Amortization of intangibles	739	2,527
Total costs and expenses	315,615	283,786
Operating income	53,556	45,781
Interest expense, net	(2,195)	(2,784)
Other expense, net	(978)	(382)
Income before income taxes	50,383	42,615
Provision for income taxes	16,162	13,424
Net income	$ 34,221	$ 29,191
Income per common share:
Basic	$ 0.37	$ 0.30
Diluted	$ 0.36	$ 0.29
Weighted average shares outstanding:
Basic	93,416	96,442
Diluted	96,199	99,451