CONSOLIDATED STATEMENTS OF OPERATIONS (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Revenues:
Research	$ 1,012,062		$ 865,000		$ 752,505
Consulting	308,047		302,117		286,847
Events	148,479		121,337		100,448
Total revenues	1,468,588		1,288,454		1,139,800
Costs and expenses:
Cost of services and product development	608,755		552,238		498,363
Selling, general and administrative	613,707		543,174		477,003
Depreciation	25,539		25,349		25,387
Amortization of intangibles	6,525		10,525		1,636
Acquisition and integration charges			7,903		2,934
Total costs and expenses	1,254,526		1,139,189		1,005,323
Operating income	214,062		149,265		134,477
Interest income	1,249		1,156		830
Interest expense	(11,216)		(16,772)		(16,862)
Other (expense) income, net	(1,911)		436		(2,919)
Income before income taxes	202,184		134,085		115,526
Provision for income taxes	65,282		37,800		32,562
Net income	$ 136,902		$ 96,285		$ 82,964
Net income per share:
Basic	$ 1.43		$ 1.01		$ 0.88
Diluted	$ 1.39		$ 0.96		$ 0.85
Weighted average shares outstanding:
Basic	96,019		95,747		94,658
Diluted	98,846	[1]	99,834	[1]	97,549	[1]

[1] During 2011, 2010 and 2009, the Company repurchased 5.9 million, 3.9 million, and 0.3 million shares of its Common Stock, respectively.