Goodwill and Other Intangible Assets, Net - Components of Goodwill and Other Intangible Assets, Net (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Finite-Lived Intangible Assets [Line Items]
Goodwill	$ 20,610
Intangible assets:
Total intangible assets	146,397	140,593
Total goodwill and intangibles assets	551,705	525,290
Accumulated amortization:
Total accumulated amortization	(59,797)	(56,207)
Goodwill and other intangible assets, net	491,908	469,083
Client lists [Member]
Intangible assets:
Total intangible assets	138,147	132,637
Accumulated amortization:
Total accumulated amortization	(54,306)	(51,016)
Other intangibles assets [Member]
Intangible assets:
Total intangible assets	8,250	7,956
Accumulated amortization:
Total accumulated amortization	(5,491)	(5,191)
Indefinite-lived Intangible Assets [Member]
Finite-Lived Intangible Assets [Line Items]
Goodwill	$ 405,308	$ 384,697