Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenues:
Total revenues	$ 1,000,502	$ 921,674	$ 3,041,828	$ 2,886,575
Costs and expenses:
Cost of services and product development	365,056	336,112	1,099,700	1,060,958
Selling, general and administrative	512,159	447,537	1,545,905	1,396,085
Depreciation	20,704	17,335	60,578	50,456
Amortization of intangibles	31,694	50,852	97,541	152,625
Acquisition and integration charges	1,742	17,114	4,156	96,342
Total costs and expenses	931,355	868,950	2,807,880	2,756,466
Operating income	69,147	52,724	233,948	130,109
Interest expense, net	(24,073)	(26,984)	(73,669)	(99,647)
Gain (loss) from divested operations	0	13,040	(2,075)	38,500
Other income (expense), net	8,024	(827)	6,953	1,193
Income before income taxes	53,098	37,953	165,157	70,155
Provision (benefit) for income taxes	11,710	26,200	(432)	31,719
Net income	$ 41,388	$ 11,753	$ 165,589	$ 38,436
Net income per share:
Basic (in dollars per share)	$ 0.46	$ 0.13	$ 1.84	$ 0.42
Diluted (in dollars per share)	$ 0.46	$ 0.13	$ 1.82	$ 0.42
Weighted average shares outstanding:
Basic (in shares)	89,846	90,854	89,947	90,969
Diluted (in shares)	90,887	92,148	91,089	92,244
Research
Revenues:
Total revenues	$ 840,998	$ 774,188	$ 2,492,427	$ 2,308,426
Conferences
Revenues:
Total revenues	66,286	57,141	259,392	214,481
Consulting
Revenues:
Total revenues	93,218	78,752	290,009	258,106
Other
Revenues:
Total revenues	$ 0	$ 11,593	$ 0	$ 105,562