Acquisitions - Additions to Goodwill, Client Lists and Other Intangible Assets Resulting from Acquisitions and Contingent Consideration Earned on Prior Period Acquisitions (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Finite-Lived Intangible Assets [Line Items]
Goodwill	$ 20,610	$ 217
Other intangible assets	293
Client lists [Member]
Finite-Lived Intangible Assets [Line Items]
Other intangible assets	$ 5,510