Acquisition and Transition Costs and Intangible Asset Amortization - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Business Acquisition [Line Items]
Acquisition and transition costs	$ 58	$ 73
Investment Banking
Business Acquisition [Line Items]
Finite lived intangible assets, amortization expenses	204	2,449
Investment Management
Business Acquisition [Line Items]
Finite lived intangible assets, amortization expenses	$ 1,790	$ 1,675