Components of Acquired Intangible Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Schedule Of Finite And Indefinite Lived Intangible Assets [Line Items]
Amortizable intangible assets, Gross Carrying Amount	$ 294,610	$ 246,586
Amortizable intangible assets, Accumulated Amortization	(65,855)	(50,695)
Amortizable intangible assets, Net Carrying Value	228,755	195,891
Indefinite-lived trademarks	89,676	89,676
Total acquired intangible assets, Gross Carrying Amount	384,286	336,262
Total acquired intangible assets, Net Carrying Value	318,431	285,567
Developed technology
Schedule Of Finite And Indefinite Lived Intangible Assets [Line Items]
Amortizable intangible assets, Gross Carrying Amount	10,640	9,819
Amortizable intangible assets, Accumulated Amortization	(9,097)	(6,288)
Amortizable intangible assets, Net Carrying Value	1,543	3,531
Customer and vendor relationships, databases
Schedule Of Finite And Indefinite Lived Intangible Assets [Line Items]
Amortizable intangible assets, Gross Carrying Amount	282,751	236,238
Amortizable intangible assets, Accumulated Amortization	(56,242)	(44,192)
Amortizable intangible assets, Net Carrying Value	226,509	192,046
Trademarks
Schedule Of Finite And Indefinite Lived Intangible Assets [Line Items]
Amortizable intangible assets, Gross Carrying Amount	969	529
Amortizable intangible assets, Accumulated Amortization	(474)	(215)
Amortizable intangible assets, Net Carrying Value	495	$ 314
Other
Schedule Of Finite And Indefinite Lived Intangible Assets [Line Items]
Amortizable intangible assets, Gross Carrying Amount	250
Amortizable intangible assets, Accumulated Amortization	(42)
Amortizable intangible assets, Net Carrying Value	$ 208