Goodwill and Intangible Assets, Net - Intangible Assets (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 191,067	$ 181,867
Accumulated Amortization	(53,158)	(37,375)
Net Carrying Amount	137,909	144,492
Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	139,767	139,767
Accumulated Amortization	(35,890)	(26,838)
Net Carrying Amount	103,877	112,929
Institutional Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	34,800	33,600
Accumulated Amortization	(16,086)	(10,398)
Net Carrying Amount	18,714	23,202
Trademarks and Trade Names [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	10,000	2,000
Accumulated Amortization	(502)	(28)
Net Carrying Amount	9,498	1,972
Licenses [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	5,000	5,000
Accumulated Amortization	(100)
Net Carrying Amount	4,900	5,000
Non-compete Agreements [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	1,500	1,500
Accumulated Amortization	(580)	(111)
Net Carrying Amount	$ 920	$ 1,389