Goodwill and Other Intangible Assets, Net - Carrying Amount of Amortizable Intangible Assets and Related Accumulated Amortization (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
Goodwill And Other Intangible Assets [Line Items]
Weighted Average Life (in years)	10 years 1 month 6 days
Gross Carrying Amount	$ 40,272	$ 40,343
Accumulated Amortization	(12,666)	(8,323)
Net Carrying Amount	27,606	32,020
Client relationships [Member]
Goodwill And Other Intangible Assets [Line Items]
Weighted Average Life (in years)	8 years 7 months 6 days
Gross Carrying Amount	23,079	23,143
Accumulated Amortization	(10,943)	(8,323)
Net Carrying Amount	12,136	14,820
Trade name [Member]
Goodwill And Other Intangible Assets [Line Items]
Weighted Average Life (in years)	15 years
Gross Carrying Amount	9,394	9,400
Accumulated Amortization	(914)
Net Carrying Amount	8,480	9,400
Software [Member]
Goodwill And Other Intangible Assets [Line Items]
Weighted Average Life (in years)	7 years
Gross Carrying Amount	7,200	7,200
Accumulated Amortization	(771)
Net Carrying Amount	6,429	7,200
Non-compete [Member]
Goodwill And Other Intangible Assets [Line Items]
Weighted Average Life (in years)	5 years
Gross Carrying Amount	599	600
Accumulated Amortization	(38)
Net Carrying Amount	$ 561	$ 600