Segment Information - Segment Profitability and Reconciliation to Net Income (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Segment Reporting Information [Line Items]
Adjusted EBITDA	$ 150,691	$ 133,149
Amortization of intangible assets	11,251	11,840
Depreciation and amortization of property, equipment and leasehold improvements	8,838	8,168
Operating income	130,602	113,141
Other expense (income), net	28,977	22,364
Provision for income taxes	28,674	30,410
Net income	72,951	60,367
Index [Member]
Segment Reporting Information [Line Items]
Adjusted EBITDA	115,637	100,049
Analytics [Member]
Segment Reporting Information [Line Items]
Adjusted EBITDA	29,536	30,360
All Other [Member]
Segment Reporting Information [Line Items]
Adjusted EBITDA	$ 5,518	$ 2,740