Schedule of Acquired Intangible Assets (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Indefinite-lived Intangible Assets [Line Items]
Gross carrying amount	$ 74,630	$ 73,685
Accumulated amortization	28,407	26,179
Net	46,223	47,506
Client Contracts And Broker Relationships
Indefinite-lived Intangible Assets [Line Items]
Gross carrying amount	59,355	58,410
Accumulated amortization	20,738	19,273
Net	38,617	39,137
Trade names
Indefinite-lived Intangible Assets [Line Items]
Gross carrying amount	2,180	2,180
Accumulated amortization	871	792
Net	1,309	1,388
Developed technology
Indefinite-lived Intangible Assets [Line Items]
Gross carrying amount	9,946	9,946
Accumulated amortization	4,959	4,316
Net	4,987	5,630
Noncompete Agreements
Indefinite-lived Intangible Assets [Line Items]
Gross carrying amount	2,012	2,012
Accumulated amortization	1,715	1,705
Net	297	307
Favorable Lease
Indefinite-lived Intangible Assets [Line Items]
Gross carrying amount	1,137	1,137
Accumulated amortization	124	93
Net	$ 1,013	$ 1,044