Components of Intangible Assets (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	$ 20,977	$ 4,333
Accumulated amortization	(4,143)	(3,082)
Net carrying amount	16,834	1,251
Client relationships
Finite-Lived Intangible Assets [Line Items]
Weighted average life at acquisition	9 years	5 years
Gross carrying amount	13,724	3,918
Accumulated amortization	(3,640)	(2,976)
Net carrying amount	10,084	942
Trade Name
Finite-Lived Intangible Assets [Line Items]
Weighted average life at acquisition	5 years	8 years
Gross carrying amount	6,372	415
Accumulated amortization	(439)	(106)
Net carrying amount	5,933	309
Noncompete Agreements
Finite-Lived Intangible Assets [Line Items]
Weighted average life at acquisition	5 years
Gross carrying amount	881
Accumulated amortization	(64)
Net carrying amount	$ 817