Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Revenues:
Total revenues	$ 994,618	$ 1,000,502	$ 2,986,644	$ 3,041,828
Costs and expenses:
Cost of services and product development	329,767	365,056	993,596	1,099,700
Selling, general and administrative	521,508	512,159	1,512,987	1,545,905
Depreciation	22,743	20,704	67,988	60,578
Amortization of intangibles	31,228	31,694	94,615	97,541
Acquisition and integration charges	1,722	1,742	5,438	4,156
Total costs and expenses	906,968	931,355	2,674,624	2,807,880
Operating income	87,650	69,147	312,020	233,948
Interest expense, net	(30,538)	(24,073)	(87,182)	(73,669)
Loss from divested operations	0	0	0	(2,075)
Loss on extinguishment of debt	(44,814)	0	(44,814)	0
Other income (expense), net	1,869	8,024	(10,046)	6,953
Income before income taxes	14,167	53,098	169,978	165,157
(Benefit) provision for income taxes	(2,797)	11,710	22,840	(432)
Net income	$ 16,964	$ 41,388	$ 147,138	$ 165,589
Net income per share:
Basic (in dollars per share)	$ 0.19	$ 0.46	$ 1.65	$ 1.84
Diluted (in dollars per share)	$ 0.19	$ 0.46	$ 1.63	$ 1.82
Weighted average shares outstanding:
Basic (in shares)	89,378	89,846	89,307	89,947
Diluted (in shares)	89,955	90,887	90,002	91,089
Research
Revenues:
Total revenues	$ 892,719	$ 840,998	$ 2,677,339	$ 2,492,427
Conferences
Revenues:
Total revenues	12,738	66,286	26,925	259,392
Consulting
Revenues:
Total revenues	$ 89,161	$ 93,218	$ 282,380	$ 290,009