Acquired Intangible Assets (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Intangible assets subject to amortization, gross carrying amount	$ 65,032	$ 56,832
Intangible assets subject to amortization, accumulated amortization	32,203	30,634
Intangible assets subject to amortization, net carrying amount	32,829	26,198
Goodwill	96,034	77,266
Trade names	46,501	42,301
Intangible assets not subject to amortization, net	142,535	119,567
Database Rights [Member]
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Intangible assets subject to amortization, gross carrying amount	22,625	15,925
Intangible assets subject to amortization, accumulated amortization	12,336	12,103
Intangible assets subject to amortization, net carrying amount	10,289	3,822
Customer Relationships [Member]
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Intangible assets subject to amortization, gross carrying amount	38,804	37,304
Intangible assets subject to amortization, accumulated amortization	16,440	15,125
Intangible assets subject to amortization, net carrying amount	22,364	22,179
Noncompete Agreements [Member]
Finite-Lived and Indefinite-Lived Intangible Assets [Line Items]
Intangible assets subject to amortization, gross carrying amount	3,603	3,603
Intangible assets subject to amortization, accumulated amortization	3,427	3,406
Intangible assets subject to amortization, net carrying amount	$ 176	$ 197