Condensed Consolidated Statements of Operations (USD $) In Thousands, except Per Share data	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Revenues:
Research	$ 250,015	$ 209,095	$ 493,450	$ 419,768
Consulting	77,962	75,760	148,592	147,399
Events	37,566	29,340	53,068	42,861
Total revenues	365,543	314,195	695,110	610,028
Costs and expenses:
Cost of services and product development	152,461	138,336	285,777	261,382
Selling, general and administrative	152,758	130,322	294,430	260,890
Depreciation	6,234	6,440	12,505	13,024
Amortization of intangibles	2,522	2,537	5,049	5,463
Acquisition and integration charges		2,330		5,841
Total costs and expenses	313,975	279,965	597,761	546,600
Operating income	51,568	34,230	97,349	63,428
Interest expense, net	(2,797)	(3,180)	(5,581)	(6,564)
Other (expense) income, net	(571)	(643)	(953)	1,109
Income before income taxes	48,200	30,407	90,815	57,973
Provision for income taxes	15,977	10,294	29,401	18,457
Net income	$ 32,223	$ 20,113	$ 61,414	$ 39,516
Income per common share:
Basic	$ 0.33	$ 0.21	$ 0.64	$ 0.41
Diluted	$ 0.32	$ 0.20	$ 0.62	$ 0.40
Weighted average shares outstanding:
Basic	96,886	95,657	96,664	95,810
Diluted	99,340	98,855	99,642	99,689